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What are Soil and its Component? Soil, the loose material that covers the land surfaces of Earth and supports the growth of plants. In general, soil is an unconsolidated, or loose, combination of inorganic and organic material. The inorganic components of soil are principally the products of rocks, and minerals that have been gradually broken down by weather, chemical action, and other natural processes. The organic materials are composed of debris from plants and from decomposition of many tiny life forms that inhabit the soil. Soils vary widely from place to place. Many factors determine the chemical composition and physical structure of the soil at any given location. The different kinds of rocks, minerals, and other geologic materials from which the soil originally formed play a role. The kinds of plants or other vegetation that grow in the soil are also important. Topography-that is, whether the terrain is steep, flat, or some combination-is another factor. In some cases, human activity such as farming or building has caused disruption. Soils also differ in color, texture, chemical makeup, and the kinds of plants they can support. Generally, soil consists of four main constituents which are mineral matter, organic matter, air, and water. Mineral water consists of two groups which is primary minerals, resistant-coarse minerals weathered from rocks, and secondary minerals, formed in the soil by recombination of substances, usually fine-grained. Organic matter derived mostly from decaying plant matter, but also consists of decaying animal matter composed of cellulose, starch and lignin in various states of decomposition. In soil that has structure, the minerals and organic component are aggregated into discrete structural unit called Peds, which are surrounded by open spaces which is occupied by air and water. In soils that are saturated, most air is removed while in freely drained soils, water adheres to the mineral particles. 1
Transcript
Page 1: Biology MAIN

What are Soil and its Component?

Soil, the loose material that covers the land surfaces of Earth and supports the growth of plants. In general, soil is an unconsolidated, or loose, combination of inorganic and organic material. The inorganic components of soil are principally the products of rocks, and minerals that have been gradually broken down by weather, chemical action, and other natural processes. The organic materials are composed of debris from plants and from decomposition of many tiny life forms that inhabit the soil.

Soils vary widely from place to place. Many factors determine the chemical composition and physical structure of the soil at any given location. The different kinds of rocks, minerals, and other geologic materials from which the soil originally formed play a role. The kinds of plants or other vegetation that grow in the soil are also important. Topography-that is, whether the terrain is steep, flat, or some combination-is another factor. In some cases, human activity such as farming or building has caused disruption. Soils also differ in color, texture, chemical makeup, and the kinds of plants they can support.

Generally, soil consists of four main constituents which are mineral matter, organic matter, air, and water. Mineral water consists of two groups which is primary minerals, resistant-coarse minerals weathered from rocks, and secondary minerals, formed in the soil by recombination of substances, usually fine-grained. Organic matter derived mostly from decaying plant matter, but also consists of decaying animal matter composed of cellulose, starch and lignin in various states of decomposition. In soil that has structure, the minerals and organic component are aggregated into discrete structural unit called Peds, which are surrounded by open spaces which is occupied by air and water. In soils that are saturated, most air is removed while in freely drained soils, water adheres to the mineral particles.

The mineral portion comes primarily in situ weathering of the geological substrate. Occasionally, however, minerals are transport in, as well as blown in from eolion wind activity. Particles range in size from very small clay particles measured in microns up to sand-size particles that can be measured in millimeters. This fraction of soil is called fine earth, and usually consists of particles less than 2mm in size. It is upon this fraction that soil texture is determined.

The volume of air and water in pore spaces is complementary, as one increase, the other decreases. In poorly drained soils, all pore space may be occupied by water while in freely drained soils, water lost from large cavities and larger pores is called gravitational water soil air differs from atmospheric air in that (1) it is saturated with water vapour (near 100% humidity) and (2) carbon dioxide, a lay-product of decomposition, is sometimes 5-10 times higher. More organic matter in a base-rich soil would favor soil fauna which deplete soil oxygen and increases soil carbon dioxide.

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Soil Formation

Soil formation is an ongoing process that proceeds through the combined effects of five soil-forming factors: parent material, climate, living organisms, topography, and time. Each combination of the five factors produces a unique type of soil that can be identified by its characteristic layers, called horizons. Soil formation is also known as pedogenesis ( from the Greek words pedon, for “ground” and genesis, meaning “birth” or “origin”).

Parent Material

The first step in pedogenesis is the formation of parent material from which the soil itself forms. Roughly 99 percent of the world’s soils derive from mineral-based parent materials that are the result of weathering, the physical disintegration and chemical decomposition of exposed bedrock. The small percentage of remaining soils derives from organic parent materials, which are the product of environments where organic matter accumulates faster than it composes. This accumulation can occur in marshes, bogs, and wetlands.

Bedrock itself does not directly give rise to soil. Rather, the gradual weathering of bedrock, through physical and chemical processes, produces a layer of rock debris called regolith. Further weathering of this debris, leading to increasingly smaller and finer particles, ultimately results in the creation of soil.

In some instances, the weathering of bedrock creates parent materials that remain in one place. In other cases, rock materials are transported far from their source-blown by wind, carried by moving water, and borne inside glaciers.

Climate

Climate directly affects soil formation. Water, ice, wind, heat and cold cause the physical weathering by loosening and breaking up rocks. Water in rock crevices expands when it freezes, causing the rocks to crack. Rocks are worn down by water and wind and ground bits by the slow movement of glaciers. Climate also determines the speed at which parent materials undergo chemical weathering, a process in which existing minerals are broken down into new mineral components. Chemical weathering is fastest in hot, moist climates and slowest in cold, dry climates.

Climate also influences the developing soil by determining the types of plant growth that occur. Low rainfall or recurring drought often discourage the growth of threes but allow the growth of grass. Soils develop in cool rainy areas suited the pines and other needle-leaf trees are low in humus.

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Living Organism

As the parent material accumulates, living things gradually gain a foothold in it. The arrival of living organisms marks the beginning of the formation of true soil. Mosses, lichens, and lower plant forms appear first. As they die, their remains add to the developing soil until a thin layer of humus is built up. Animals’ waste materials add nutrients that are used by plants. Higher forms of plants are eventually able to establish themselves as more and more humus accumulates. The presence of humus in the upper layers of a soil is important because humus contains large amounts of the elements needed by plants.

Living organisms also contribute to the development of soils in other ways. Plants build soils by catching dust from volcanoes and deserts, and plants’ growing roots break up rocks and stir the developing soil. Animals also mix soils by tunneling in them.

Topography

Topography, or relief, is another important factor in soil formation. The degree of slope on which a soil forms helps to determine how much rainfall will run off the surface and how much will be retained by the soil. Relief may also affect the average temperature of a soil, depending on whether or not the slope faces the sun most of the day.

Time

The amount of time a soil requires to develop varies widely according to the action of the other soil-forming factors. Young soils may develop in a few days from the alluvium (sediments left by floods) or from ash from volcanic eruptions. Other soils may take hundreds of thousands of years to form. In some areas, the soils may be more than a million years old.

Horizons

Most soils, as they develop become arranged in a series of layers, known as horizons. These horizons, starting at the soil surface and proceeding deeper into the ground, reflect different properties and different degrees of weathering.

Soil scientists have designated several main types of horizons. The surface horizon is usually referred to as the O layer; it consists of loose organic matter such as fallen leaves and other biomass. Below that is the A horizon, containing a mixture of inorganic mineral materials and organic matter. Next is the E horizon, a layer from which clay, iron, and aluminum oxides have been lost by a process known as leaching (when water carries materials in solution down from one soil level to another).

Removal of materials in this manner is known as eluviations, the process that gives the E horizon its name. Below E horizon is the B horizon, in which most of the iron, clay, and other leached materials have accumulated. The influx of such materials is called illuviation. Under that layer is the C horizon, consisting of partially weather bedrock, and last, the R horizon of hard bedrock.

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Along with these primary designations, soil scientists use many subordinate names to describe the transitional areas between the main horizons, such as Bt horizon or BX2 horizon.

Soil scientists refer this arrangement of layers stop another as a soil profile. Soil profiles change constantly but usually very slowly. Under normal conditions, soil at the surface is slowly eroded but is constantly replaced by new soil that is created from the parent material in the C horizon.

Why Is Soil So Important?

Soil is important for plants because it holds roots, stores nutrients, and provides support for plants. Most living things need three basic things to survive: food, water, and air. Plants get their nutrients and water from soil. Although all green plants make their food by photosynthesis, they also need to get nutrients from the soil. These nutrients dissolve in water and are taken up by the roots of the plant.

The most important plant nutrients are nitrogen (N), phosphorus (P), and potassium (K). Nitrogen helps above-ground leafy growth and gives dark green color to leaves. Phosphorus encourages plant cell division. Without phosphorus, flowers and seeds could not form. Phosphorus also helps root growth and protects the plant from disease. Like phosphorus, potassium increases the plant’s resistance to disease and encourages root growth. Potassium is needed for the production of chlorophyll.

Physical Properties of Soil

Soil texture is the determination of the percentages of sand, silt and clay:-

Sand has large particles with little surface area. Sand has very limited chemical and physical bindings with particles in the soil.Silt is smaller than sand and larger than clay. Silts are more weathered than sand. Silt has less surface area than clay. Because of silt’s size and physical properties, they can hold water and nutrients.Clay is the smallest of the three particles sizes. It has strong affinity for water and nutrients. Clay has thousands of times more surface area than silt and millions more times the surface area of sand.

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A soil that tested by Western Laboratories is dried, ground and passed through a 2 mm sieve. Particles sizes greater than 2 mm fall in the gravel, pebble, and cobble classes. Particles smaller than 2mm (size of a pinhead) are considered as soil. By feel, sand is gritty, silt is very slick and clay is very sticky. There are over a million combinations of percent sand, percent silt and percent clay. Sand, silt and clay form textural classes when mixed in differing percentages. In naming textural classes, the last word is the domination fraction. Soil textural classes are derived from a textural triangle. When using textural triangle the percentages of sand, silt and clay should total 100.

Loam – means sand silt and clay fraction are all shared in this class.Loamy Sand – means sand is the dominating fraction, but silts and clays are

present.Sandy Loam – means silts and clays are present, but sand dominates.

Farmers refer to texture as (1) Light soils being coarse textured (2) Heavy soils being fine textured. Light soils are easier to work. They are more seriated. They hold less moisture. They have more temperature fluxuation between day and night. They have lower organic matter. They also have higher nutrient leaching potential. Heavy soils are harder to work. The soil structure can be altered. They hold more moisture and the soil temperature fluctuates less. They have higher biological activity and organic matter. They have lower nutrient leaching potential.

Soil texture and soil structure have strong influences on soil aggregation. A well aggregated soil improve soil air, water penetration, nutrient assimilations, soil gas evacuation, soil drainage, root development and microorganism activity. Soil structure is the way the sand; silt and clay are arranged or grouped together to form structures. Typer of soil structures are:

Prismlike – aggregates with horizontal axes are shorter than the vertical axes. Think of a quartz prism. This structure is found in young soils or in dry and arid

regions.Blocklike – aggregates with horizontal axes and vertical axes are more or less equal. Like

the toy building blocks or a small sugar cube. Blocklike structure is found deep in the soil horizon (profile).

Platelike – aggregates with horizontal axes longer than the vertical, like a dinner plate or Frisbee. This structure occurs on or near the soil surface caused by

ponded water or impact from rain (crusting).Spheroidal – aggregates that are more or less rounded; granular, crumb like. This

structure is found under grass stands near the surface.

Improper soil structure management affects the physical, chemical and biological properties. By destroying structure, the solid phase of the soil increase at the expense of air and water. The chemical and biological phase is affected because the soil is compacted. This affects root growth and biological activity. Soil consistence is the resistance of a soil to deformation or rupture by a compressing, shearing or pulling force. Consistence is a measure of how soil particles bind together (cohesion), bind with organic matter (adhesion), and how the soil responds to tillage under different moisture contents.

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In most cases, soil color can be attributable to organic matter or to the state of oxidation and hydration of the iron minerals present.

Whitish soils are associated with various salts in arid and semiarid regions.Black and dark brown colors indicate accumulation of organic matter usually confined to the surface horizons.Gray colors are associated with the removal of iron.Reddish-brown colors are associated with well-drained soils.

Soil color is described using the Munsell color system which uses hues (red R or yellow Y), value (darkness or lightness from white to black), and chroma (the strength of the color).

Chemical Properties of Soil

Soils also have key chemical characteristics. The surfaces of certain soil particles, particularly the clays, hold groupings of atoms known as ions. These ions carry a negative charge. Like magnets, these negative ions (called anions) attract positive ions (called cations). Cations, including those from calcium, magnesium, and potassium, then become attached to the soil particles, in a process known as cation exchange. The chemical reactions in cation exchange make it possible for calcium and the other elements to be exchanged into water-soluble forms that plants can use for food. Therefore, a soil’s cation exchange capacity is an important measure of its fertility.

What is Ecology?

The term ecology originated from the Greek word oikos, which means dwelling and logos which means the study of something. Based on this, the term ecology can be described as the study of the habit of the living thing. Various definitions have been suggested for this term such as:-

Ecology is the study of relationship between organisms in their natural habitat.Ecology is the study of organism relating to their natural environment.Ecology is the study of interactions between organism and their habitat (Ernst Haekel, 1969).Ecology is the study of structure and function of the natural habitat as a part of it.Ecology is the study of the sum total of relationship between living thing and their habitat. (Webster’s Unabridged Dictionary).

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The best understanding of the concept of ecology is based on hierarchy or organization of life in biology. According to the organization of life:-

Molecules of life are organized specifically to form cells.Cells are then grouped together to form different tissues.Tissues then arranged to form functional organ varies in structure and function.Existence of these function forms varies type of system such as blood circulation system.Arrangement of all this system is considered as constitutes a complete organism.Individual of one type of organism do not live in isolation but in groups called populations.Various populations of organism interact with one another forming a community.A community including abiotic factors and interacts with it is called ecosystem.

All ecosystems on earth together constitute the biosphere that encompasses all the layers, air, water and soil, from the base of the ocean to the atmosphere and extending mot more than 15 km from the surface of the earth. In the biosphere, organism is distributed according to fixed patters that are clearly seen on the global scale as large and stable vegetation zones. Example for these kinds of zones including tropical rainforest, temperate grassland, deciduous temperate forest, coniferous forest and etcetera. Each of these zones is called biome. Each biome represents a primary life zone characterized by the presence of dominant plants form.

Based on the hierarchy or organization of life, ecology is a study of biological organization levels that higher than individual organism, that is population, communities, ecosystem and biospheres.

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Division in the Field of Ecological Studies

Basically, study of ecology covers widely various branches of science such as taxonomy, physiology, geology, chemistry, physic, animal behavior and sociology. Generally ecology can be divided into plant ecology and animal ecology. Scope of ecological study can be further subdivided into various divisions such as:-

Habitat ecology such as marine ecology, freshwater ecology, estuarine ecology and terrestrial ecology.Ecosystem ecology which is related to the relationship between biotic and abiotic component in an ecosystem.Production ecology which is related to the aspects of energy transfer in a system, the flow of energy through organism and the rate of increase of organic composition and organism.Paleontology which is related to the geological environment of fossil organism.Preservation ecology which is related to the efficient and effective management of the natural resources to increase their production.

Ecological study also can be divided into two parts as follows:-Autecology’s is related to the study of the relationship between individual organism, populations or species and the environment. Here the focus is on the life cycles and organism behaviors as an adaptation to the environment.Synecology’s is related to the study of groups of groups of organisms that combine to form a whole unit.

As such, studies carried out on one relationship, for example shorea with its natural environment, must take the autecological approach. On the contrary, if the study is related to the forest in whish the shorea plants live, the study approach must be synecological. It must be emphasized that the division of ecology into a number of detailed divisions is solely to facilitate studies, but they all exist as a whole in the natural environment.

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1.1 Objective of Soil Ecology

Primary research initiatives involve evaluating the properties of soil which define soil quality and assessing the capability of implementing soil remediation procedures to optimize the soil quality level. The overall objective of these studies is to derive principles applicable to assessment and management of industrially contaminated soil sites. The product of the optimized soil quality will be improvement of both ecosystem quality and overall environmental health. Specific research areas include:-

Elucidation of the properties of soil controlling microbial movement and function of soil: For successful bioremediation of soil system, microbes capable of catalyzing the requisite processes (frequently, genetic engineered bacteria) may be added to the soils in which their action is needed. To achieve this objective, bacterial propagules must be amended to soil surface and washed through the soil pores to the sites where their function is required. The properties of soil and of bacteria controlling transport of microbes ore being evaluated. These studies include a micro morphological evaluation of soil to determine the components of soil to which foreign bacteria become associated when washed into soil pores and elucidation of the properties of soil controlling function and survival of the bacterial propagulas.Evaluation of the recovery of soil quality in heavy metal impacted soils: High metal loadings reduce soil biological activity and therefore result in a reduction of overall ecosystem health. The capacity to ameliorate the impact of metal contamination on soil biological function and to optimize soil quality through a variety of remediation procedures is being evaluated.Development of methods to manage soil quality in sites contaminated with biodegradable carbonaceous substances: The capacity to optimize soil quality in systems contaminated with petroleum products undergoing a variety of remediation procedures is being assessed. Recovery of soil biological activity, reduction of toxicity, and recovery of soil structure are being evaluated.

Other research activities include study of a (a) the behavior of xenobiotics and native organic compounds in soil and their impact on ecosystem stability and (b) biogeochemical cycles in native ecosystems and the factors controlling these processes. The studies of the behavior of xenobiotics in soils have involved the examination of reclamation and management practice for disturbed soils, behavior of antibiotics and various carcinogens in soils, and problem associated with disposal of radioactive wastes. Objectives of the biogeochemical cycle projects relate to the elucidation of the responsible microbial populations, determination of the enzymes involved in the mineralization reactions, evaluation of the rates of plant nutrient movement through various soil organic matter pools (including the effect of various management systems on this nutrient mobility), and delineation of plant-microbe interactions affecting nutrient cycles.

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Soil is generally considered (and treated as) a lifeless substance, but the opposite is true: Soils teem with life, and would not exist without the organisms inhabiting it. Under a 1-meter-square soil surface, more than 10,000 bacterial and fungal types may be found, as well as 100 to 1,000 species of soil animals, such as protozoa, nematodes, mites, collembolan, and earthworms. These organisms form an integral part of the soil, as they contribute to the development of soil structure, the dynamics of organic matter, and the availability of nutrients for plant growth.

The objective of this ecological study is to study soil organisms at the population, community and ecosystem level also to ultimately increase understanding of the role of soil organisms. An important focus in this theme is on the significance of soil organisms for nutrient use efficiency, disease suppression, and soil structure formation. Current research questions relate to the structure and function of soil biodiversity: How is soil biodiversity maintained, what are the linkages vegetation diversity, what is its function, and can we use this knowledge in the development of sustainable agriculture? A second important research topic is the effect of environmental stressors (such as metals, PACs and injected manure) on soil organism activity. Ultimately, such knowledge will be applied in the development of a biological indicator of soil quality.

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1.2 Importance of Ecological Study

The importance of the knowledge obtained from ecological studies includes the following:

Initiate us to understand the roles and function of an ecosystem. This is based on the facts that the plants and animals complex in a community is the sum total of the interrelationships between organisms and their physical environment.Facilitate us to understand the concepts of natural population control.With the development of improved sampling methods, the study of natural populations of organisms can be carried out more accurately.Make possible the management of chemical control on animal pest such as insects, to be carried out more effectively.Enable us to understand the life system of a species. This way, primary mortality factors in a natural population is known. This further allows us to develop control measures that least affects the balance of the natural environment.With the knowledge of the effects of physical environmental factors on the development and physiology of individual organism, the upper and lower mortality limits can be determined.Through the study of genetic changes in the species, the process the evolution can be understood to a greater depth.

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What is Soil Analysis?

The idea behind balance plant nutrition is to apply nutrients that cannot be adequately supplied by the soil. We therefore need to use soil analysis to determine how much of each nutrient the soil will provide to our crop.

Soils often contain high amounts of nutrients, but the majority is in solid forms. Plants take up nutrients in solution: therefore most of the solid nutrients may be unavailable. For example, a soil may contain 5,000 lbs of potassium per acre, but only 50 lbs may be available to a crop.

The trick to soil analysis is to determine both the amount of each nutrient that is immediately available and the amount that can become available during the life of the crop. Various methods have been developed and the key to success is that the methods must be calibrated.

Experiments must be done to show that the result of the analysis consistently indicate the amount of nutrient that a crop will actually get from the soil. Once the method and its interpretation are shown to be reliable, they can then be used to predict whether or not a crop will need additional nutrients and how many needs to be added.

The numbers on a soil report do not indicate the exact amount of nutrients available to a crop, but when interpreted correctly, they give a description of the soil fertility. The potassium analytical result may be 0.25 meq/100 cm3, but this number does not mean anything by itself. What really matters is that for our method, this value indicates that the potassium level is deficient.

Another laboratory may use a different method and get a different potassium value on the same sample. The results from the two laboratories cannot be directly compared. However, if they are both properly calibrated, the two methods should give the same fertility description; they should both indicate that the soil is deficient in potassium.

The analytical result is used to suggest how much nutrient should be applied. The exact amount needed will depend on the crop to be grown and must be modified to suit the conditions under which it is grown.

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2.1 Soil Sampling Technique

Any technique that is used for soil sampling must be one that maintains the soil sample in its natural condition so that the results obtained from its study illustrate the actual characteristics of the soil. Methods that are usually used for soil sampling include:-

The use of soil bore (figure 2.10). Using this methods, soil samples can be obtained from various depths. As such, this method is suitable for the study of the characteristic of the different layers of a specific soil profile.The use of a corer. An example of a corer is the ‘apple-corer’ type (figure 2.11). Through this method, a soil sample is isolated by puling out the piston from its cylinder. Using this method, a large portion of the natural structure of the soil is maintained in its original state.The use of the scoop. Like the soil bore, this tool can be used to obtain soil samples from different depths. However, using this method may cause various problem besides it’s a difficult technique and also may destroy the soil area being studied.

Figure 2.10 Soil Bore

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EXPERIMENT 2.1 Soils Sampling Techniques

Purpose: Soil Sampling Using Apple-Corer type Corer TechniqueApparatus:

Metal Cylinder and Piston (to dig out soil) Newspapers

Figure 2.11 ‘Apple-Corer’ types Corer

Procedure

1. Carefully press the metal cylinder into the land contains soil (terrestrial area).2. Soils that contain in the metal cylinder then dig out from that area.3. The soil is removed from the cylinder by using the piston.

Discussion

1. We must be very careful when dig and take out the soil sample in order to maintain its natural and original state.

2. Soil sample must not be pressed or crashed.

Conclusion

Using the appropriate technique and methods will prevent any kind of distraction or damage on the sample which will be used in the ecological study.

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2.2 DETERMINATION OF THE TEXTURE OF SOIL USING MECHANICAL ANALYTSIS

A Piece Of Information

Soil texture is determined by the relative amounts of three groups of soil particles, namely sand, silt and clay. Texture provides a means to physically describe soil by feel.

The texture of soil determines the amounts of air and water the soil can hold. Plant roots need liberal supplies of both. Large soil particles do not pack tightly and therefore provide air spaces in the soil. On the other hand, soil consisting of extremely fine pack tightly and permits little air in the soil to support root function. A soil with a very large particles drains to extensively and plants will lack sufficient water, will wilt, and perhaps even die. A soil with extremely fine particles holds tremendous amounts and can hold so much as to exclude air from the soil. In the case, the roots die, the plants wilt, and perhaps will die as well. Thus the perfect soil texture for growing plants is a compromise between fine, medium, and coarse particles.

Sand has large particles with little surface area. Sand has very limited chemicals and physicals bindings with particles in the soil.

Silt is smaller than the sand and larger than clay. Silts are more weathered than sand. Silt has less surface area than clay. This is because of it’s size and physical properties, they can hold water and nutrient.

Clay is the smallest of the three particles size. It has strong affinity for water and nutrients. Clay has thousands of time or more surface area of sand. It doesn’t let air and water passing through it well.

The relative sizes for three types of soil particles is shown in Table 2.21

Soil Particles Diameter Of Soil Particles (mm)

Stones/ Gravels >2.0

Coarse Sand 2.0-0.2

Fine Sand 0.2-0.02

Silt 0.02-0.002

Clay <0.002

TABLE 2.20 : size ranges of soil particles according ISSS (International Soil science Society ) standard.

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*Stones (gravels are not considered to be soil particles. ) By feel, sand is gritty, silt is very slick or floury and clay is very sticky when wet.

There are million combinations of percent sand, percent silt and percent clay. Sand, slit, and clay from textural classes when mixed in differing percentages. In naming textural classes, the last word is the dominating fraction.

Loam --- means sand, silt and clay fraction are all shared in the class.

Loamy sand --- means sand is the dominating fraction, but silt and clay present.

Sandy loam --- means silts and clay are present, but sand dominates.

Soil textural classes are derived from a textural triangle. When using a textural triangle, the percentage of sand, slit, and clay should total 100.

Figure 2.20: A Textural triangle

Farmers refer to texture as:

Light soils being coarse textured. Heavy soils being fine textured.

Light soils are easier to work. They are more aerated. They hold less moisture. They have more temperature flocculation between day and night. They have lower organic matter. They also have higher nutrient leaching potential.

Heavy soils are harder to work. The soil structure can be altered. They hold more moisture and the soil temperature fluctuates less. They have higher biological activity and organic matter. They have lower nutrient leaching potential.

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Soil texture and soil structure have strong influences on soil aggregation. A well-aggregated soil improves soil air, water penetration, root growth, and nutrient as simulation, soil gas evacuation, soil drainage, root development and microorganisms’ activity.

Soil structure is the way sand, silt, and clay are arranged or grouped together to form structures. Each individual unit of soil structure called a pad. Types of soil structure are:

Prism like ---aggregates with horizontal axes are shorter than vertical axes. Think of a quartz prism. This structure is found in young soils or in dry and arid regions.

Block like---aggregates with horizontal axes and vertical are more or less equal. Like the toy building blocks or a small sugar cube. Block like structure is found deep in the soil horizon.

Plate like ---aggregates with horizontal axes longer than the vertical, like a dinner plate or Frisbee. This structure occurs on or near the soil surface caused by ponded water or impact from rain.

Spheroid ----aggregates that are more or less rounded, granular, crumb like. This structure is found under grass stands near the surface.

Shapes Of Soil Aggregates

FIGURE 2.21: Shapes of soil aggregate

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Improper soil structure management affects the physical, chemical and biological properties. By destroying structure, the solid phase of soil increases at the expense of air and water. The chemical and biological phase is affected because the soil is compacted. This affects root growth and biological activity.

Soil consistence is the resistance of soil to deformation or rapture by a compressing, shearing or pulling force. Consistence is a measure of how soil particles bind together, bind with organic matter, and how the soil responds to tillage under different moisture contents.

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EXPERIMENT 2.2

Purpose: To determine the texture of a soil sample.

Apparatus: Four sieves with 2mm, 0.2mm, and 0.02mm mesh openings respectively,

newspaper, plastic bags, rubber gloves, 4 beakers, electronic balance, oven and crucibles.

Materials: Soil sample A, B, and C

Procedure: 1. All the soil samples are dried in oven at 101oc-105oc.

2. A sieves with 2mm mesh openings are put on a large piece of newspaper and the soil sample A is poured on the sieve (a).3. The sieve is shaken carefully until no soil particles are coming out

through the openings. Soil particles that stay on top of the sieve is collected and its mass with beaker is recorded as (b).

4. Sieved soil particles on the newspaper are collected and are put onto another sieve with 0.2mm openings. Step (2) and (3) are repeated to find the mass of another type of soil particles.

5. Step (4) is repeated for sieves with 0.02mm and 0.002mm mesh openings.

6. Sieved soil particles on the newspaper sieves with 0.002mm mesh opening are clay. Its mass with beaker (f) is recorded.

7. All the data obtained are performed in Table 2.2.8. The textural classes for each soil sample are determined.

Types of mesh

FIGURE 2.22 : Sieves with different size of mesh openings

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Result:

No. Mass of /g Soil Sample A Soil Sample B Soil Sample C1. Soil sample, a 444.27 153.30 584.842. Beaker + stones, b 97.86 174.17 150.823. Beaker + coarse sand, c 210.97 153.96 295.204. Beaker + fine sand, d 165.04 107.83 128.335. Beaker + slit, e 242.24 111.33 155.036. Beaker + clay, f 199.91 110.28 121.197. Beaker, g 94.35 100.85 96.558. Stones, b-g 3.51 73.32 54.279. Coarse sand, c-g 116.62 53.13 198.6510. Fine sand, d-g 70.69 6.96 31.7811. Slit, e-g 147.89 10.46 58.5012. Clay, f-g 105.56 9.43 241.64

TABLE 2.21 : Masses of stones, sand, slit and clay components of soil sample.

No. Percentage of / % Soil sample A Soil sample B Soil sample C1. Stones 0.79 47.83 9.282. Sand 42.16 39.20 39.403. Slit 33.29 6.82 10.004. Clay 23.76 6.15 41.32

TABLE 2.22: Percentage of stones, sand, silt, and clay components of soil sample.

No. Percentage of / % Soil sample A Soil Sample B Soil sample C1. Sand 42.50 75.13 43.432. Slit 33.55 13.08 11.033. Clay 23.95 11.79 45.54

Table 2.23: Relative percentage of sand, slit, and clay components of soil sample

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Percentage of soil Mass of soil component Component Mass of soil sample= X 100%

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FIGURE 2.23: The textural classes for soil sample A is loam

FIGURE 2.24: The textural classes for soil sample B is loamy sand

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FIGURE 2.25: The textural classes for soil sample C is sandy clay.

Discussion: 1. All the soil samples need to be dried up first so that the soil particles can be sieved easily.

2. The relative percentage of sand, slit and clay must be determined to complete the soil textural triangle as shown above. This is because stone are not considering as a type of soil particles.

Conclusion:

The textural classes for soil sample A, B, C are loam, loamy sand and sandy clay respectively.

2.3 Organic Matter and Humus of Soil

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Organic Matter and Humus of Soil

Understanding the role that soil organism's play is critical to sustainable soil management. Based on the understanding, focus can be directed toward strategies that build both the numbers and the diversity of soil organism. Like cattle and other farm animals, soil livestock require proper feed. That feed comes in the form of organic matter

Organic matter and humus are term that describes somewhat different but related things. Organic matter refers to fraction of the soil that is composed of both living organisms and once-living residues in various stages of decomposition. Humus is only a small portion of the organic matter. It is the end product of organic matter decomposition and is relatively stable.

Further decomposition of humus occurs very slowly in both agricultural and natural settings. In natural systems, a balance is reached between the amount of humus formation and the amount of humus decay this balance also occurs in most agricultural soil, but often at a much lower level of soil humus. Humus contributes to well-structured soil that, in turn, produces high-quality plants. It is clear that management of organic matter and humus is essential to sustaining the whole soil ecosystem.

The benefits of a topsoil rich in organic matter and humus are many. They include rapid decomposition of crops residues, granulation of soil into water-stable aggregates, decreased crusting and cladding; improve internal drainage, better water infiltration, and increased water and nutrient holding capacity. Improvements in the soil's physical structure facilitate easier tillage, increased water storage capacity, reduced erosion, better formation and harvesting of root crops, and deeper, more prolific plant root systems.

Soil organic matter can be compared to a bank account for plant nutrients. Soil containing 4% organic matter in the top seven inches has 80,000 pounds of organic matter per acre. Those 80,000 pounds of organic matter will contain about 5.25% nitrogen, amounting to 4,200 pounds of nitrogen per acre. Assuming a 5% release rate during the growing season, the organic matter could supply 210 pounds of nitrogen to a crop. However, if the organic matter is allowed to degrade and lose nitrogen, purchased fertilizer will be necessary to prop up crop yields.

All the soil organisms mentioned previously, except algae, depend on organic matter as their food source. Therefore, to maintain their populations, organic matter must be renewed from plants growing on the soil, or from animal manure, compost, or other materials imported from off site. When soil livestock are fed, fertility is built up in the soil, and the soil will feed the plants.

Ultimately, building organic matter and humus levels in the soil is a matter of managing the soil's living organisms- something akin to wildlife management or animal husbandry.

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This entails working to maintain favourable conditions of moisture, temperature, nutrients, pH, and aeration. It also involves providing a steady food source of raw organic material.

Soil Tilth Organic Matter

A soil that drains well, does not crust, takes in water rapidly, and does not make clods is said to have good tilth. Tilth is the physical condition of the soil as it relates to tillage ease, seedbed quality, easy seeding emergence, and deep root penetration. Good tilth is dependent on aggregation-the process whereby individual soil particles are joined into clusters or "aggregates".

Aggregates form in soils when individual soil particles are oriented and brought together through the physical forces of wetting and drying or freezing and thawing. Weak electrical forces from calcium and magnesium hold soil particles together when the soil dries. When this aggregates become wet again, however, their stability is challenged, and they may break apart. Aggregates can also be held together by plant roots, earthworm activity, and by glue-like products produced by soil micro organisms. Earthworm-created aggregates are stable once they come out of the worm. An aggregates formed by physical forces can be bound together by fine root hair or threads produced by fungi.

Aggregates can also become stabilized (remain intact when wet) through the by-product of organic matter decomposition by fungi and bacteria chiefly gums, waxes, and other glue-like substances. These by-products cement the soil particles together, forming water-stable aggregates (figure2.30). The aggregate is then strong enough to hold together when wet-hence the term “water-stable”.

USDA soil microbiologist Sara Wright named the glue that holds aggregates together “glomalin” after the Glom ales group of common root-dwelling fungi. These fungi secrete a gooey protein known as glomalin through their hair-like filaments, or hyphae. When Wright measured glomalin in soil aggregates she found levels as high as 2% of their total weight in eastern U.S. soil. Soil aggregates from the West and Midwest had lower levels of glomalin. She found that tillage tends to lower glomalin levels. Glomalin levels and aggregation were higher in no-till corn plot than in tilled plots. Wright has a brochure describing and how it benefits soil, entitled Glomalin, Manageable Soil Glue. To order this brochure sees the Additional Resources _section of this publication.

Figure (2.30)

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Well-aggregated soil allows for increased water entry, increased air flow, and increased water-holding capacity. Plant roots occupy a larger volume of well-aggregated soil. High in organic matter, as compared to a finely pulverized and dispersed soil, low in organic matter. Roots, earthworms, and soil arthropods can pass more easily through a well-aggregated soil. Aggregated soil also prevents crusting of the soil surface. Finally, well-aggregated soils are more erosion resistant, because aggregates are much heavier than their particles components. For a good example of the effect of organic matter additions on aggregation, as shown by subsequent increase in water entry into the soil, see table 2.31.

Manure rate(tons /acre)

Inches of water

0 1.28 1.916 2.7

Table 2.30 Water entry into the soil after 1 hour

The opposite of aggregation is dispersion. In the dispersed soil, each individual soil particle is free to blow away with the wind or wash away with overland flow of water. Clay soils with poor aggregation tend to be sticky when wet, and cloddy when dry. If the clay particles in these soils can be aggregated together, better aeration and water infiltration will result. Sandy soils can benefit from aggregation by having a small amount of dispersed clay that tends to stick between the sand particles and slow the downward movement of water.

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Crusting is a common problem on soils that are poorly aggregated. Crusting results chiefly from the impact of falling raindrops. Rainfall causes clay particles on the soil surface to disperse and clog the pores immediately beneath the surface. Following drying, a sealed soil surface result in which most of the pore space has been drastically reduced due to clogging from dispersed clay particles. Subsequent rainfall is much more likely to run off than to flow into the soil (figure 2.31)

Since raindrops start crusting, anyManagement practices that protect the soil fromTheir impact will decrease crusting and increaseWater flow into the soil. Mulches and cover cropsserve this purpose well, as do no-till practices,which allow the accumulation of surface residue.Also a well-aggregated soil will resist crusting because the water-stable aggregates are less likelyto break apart when the raindrop hits them. Figure 2.31

Long-term grass production produces thebest-aggregated soils. A grass sod extends a massof fine roots throughout the topsoil, contributing to the physical processes that help formaggregates. Roots continually remove water fromsoil micro sites, providing local wetting anddrying effects that promotes aggregation. Fineroot hairs also bind soil aggregates together.

Roots also produce food for soilmicroorganisms and earthworms, which in turn generate compounds that bind soil particles intowater-stable aggregates. In addition, perennialgrass sods provide protection from raindrops anderosion. Thus, a perennial cover creates acombination of conditions optimal for thecreation and maintenance of well-aggregated soil.

Conversely, cropping sequences thatinvolve annual plants and extensive cultivationprovide less vegetative cover and organic matter,and usually result in a rapid decline in soilaggregation.

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Farming practices can be geared to conserve and promote soil aggregation. Because the binding substances are themselves susceptible to microbial degradation, organic matter needs to be replenished to maintain microbial populations and overall aggregated soil status. Practices should conserve aggregates once they are formed, by minimizing factors that degrade and destroy aggregation. Some factors that destroy or degrade soil aggregates are:

bare soil surface exposed to the impact of raindrops

removal of organic matter through crop production and harvest without return the organic matter to the soil

excessive tillage

working the soil when it is too wet or too dry

use of anhydrous ammonia, which speeds up decomposition of organic matter

excess nitrogen fertilization

allowing the build-up of excess sodium from irrigation or sodium- containing fertilizers

Table 2.31 Factors that Destroy or Degrade Soil Aggregates.

Tillage, Organic Matter, and Plant Productivity

Several factors affect the level of organic matter that can be maintained in a soil. Among these are organic matter additions, moisture, temperature, tillage, nitrogen levels, cropping and fertilization. The level of organic matter present in the soil is a direct function of how much organic material is being produced or added to the soil versus the rate of decomposition. Achieving this balance entails slowing the speed of organic matter decomposition, while increasing the supply of organic materials produced on site and / or added from off site.

Moisture and temperature also profoundly affect soil organic matter levels. High rainfall and temperature promote rapid plant growth, but these conditions are also favourable to rapid organic matter decomposition and loss. Low rainfall or low temperatures slow both plant growth and organic matter decomposition. The native Midwest prairie soils originally had a high amount of organic matter from the continuous growth and decomposition of perennial grasses, combined with a moderate temperature that did not allow for rapid decomposition of organic matter. Moist and hot tropical areas may appear lush because of rapid plant growth, but soils in these areas are low in nutrients. Rapid decomposition of organic matter returns nutrients back to the soil, where they are almost immediately taken up by rapidly growing plants.

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Tillage can be beneficial or harmful to a biologically active soil, depending on what type of tillage is used and it is done. Tillage affects both erosion rates and soil organic matter decomposition rates. Tillage can reduced the organic matter level in croplands below 1% rendering them biologically dead. Clean tillage involving molboard plowing and disking breaks down soil aggregates and leaves and soil prone to erosion from wind and water.

The mouldboard blow can bury crop residue and topsoil to a depth of 14 inches. At this depth, the oxygen level in the soil is so low that decomposition can not proceedAdequately. Surface-dwelling decomposer organisms suddenly find themselves suffocated and soon die. Crop residues that were originally on the surface but now have been turn under will putrefy in the oxygen-deprived zone. This rotting activity may give a putrid smell to the soil. Furthermore, the top few inches of the field are often covered with subsoil having very little organic matter content and, therefore, limited ability to support productive crop growth.

The topsoil is where the biological activity happens-it’s where the oxygen is. That’s why a fence post rots off at the surface. In terms of organic matter, tillage is similar to opening the air vents on a wood-burning stove; adding organic matter is like adding wood to the stove. Ideally, organic matter decomposition should proceed as an efficient burn of the ‘wood’ to release nutrients and carbohydrates to the soil organisms and create stable humus. Shallow tillage incorporates residue and speeds the decomposition of organic matter by adding oxygen that microbes need to become more active.

In cold climates with a long dormant season, light tillage of a heavy residue may be beneficial; in warmer climates it is hard enough to maintain organic matter levels without any tillage. As indicated in, molboard plowing causes the fastest decline of organic matter, no-till the least. The plow lays the soil up on its side, increasing the surface area exposed to oxygen. The other three types of tillage are intermediate in their ability to foster organic matter decomposition.

Oxygen is the key factors here. The molboard plow increases the soil surface area, allowing more air into the soil and speeding the decomposition rate. The horizontal line on represents the replenishment of organic matter provided by wheat stubble. With the molboard plow, more than entire organic matter contribution from the wheat straw is gone within only 19 days following tillage. Finally, the passage of heavy equipment increases compaction in the wheel tracks, and some tillage implements themselves compact the soil further, removing oxygen and increasing the change that deeply buried residues will putrefy.

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Tillage also reduced the rate of water entry into the soil by removal of ground cover and destruction of aggregates, resulting in compaction and crusting. Table 2.33 shows three different tillage methods and how they affect water entry into the soil. Notice the direct relationship between tillage type, ground cover, and water infiltration. No-till has more than three times the water infiltration of the molboard-plowed soil. Additionally, no-till fields will have higher aggregation from the organic matter decomposition on site. The surface mulch typical of no-till fields acts as a protective skin for the soil. This soil skin reduces the impact of raindrops and buffers the soil from temperatures extremes as well as reducing water evaporation.

Water Infiltration mm/minute

Ground cover percent

,No-till 2.7 48Chisel Plow 1.3 27Moldboard Plow 0.8 12 From Boyle et al. 1989.

Table 2.31 Tillage effects on water infiltration and group cover.

Both no-till and reduced tillage systems provide benefits to the soil. The advantages of a no-till system include superior soil conservation, moisture conservation, reduced water runoff, long-term build up of organic matter, and increased water infiltration. A soil managed without tillage relies on soil organisms to take over the jod of plant residue incorporation formerly done by tillage. On the down side, no-till can foster a reliance on herbicides to control weeds and can lead to soil compaction from the traffic of heavy equipment.

Pioneering development work on chemical-free no-till farming is proceeding at several research stations and farms in the eastern U.S. Pennsylvania farmer Steve Groff has been farming no-till with minimal or no herbicides for several years. Groff grows cover crops extensively in his fields, rolling them down in the spring using a 10-foot rolling stalk chopper. This rolling chopper kills the rye or vetch cover crop and creates nice no-till mulch into which he plants a variety of vegetable and grain crops. After several years of no-till production, his soils are mellow and easy to plant into Groff farms 175 acres of vegetables, alfalfa, and grain crops on his Cedar Meadow Farm. Learn more about his operation in the Farmer Profiles section of this publication, by visiting his Web site, or by ordering his video (see Additional Resources section ).

Other conservation tillage systems include ridge tillage, minimum tillage, zone tillage, and reduced tillage each possessing some of the advantages of both conventional till and no-till. These systems represent intermediate tillage systems, allowing more flexibility than either a no-till or conventional till system might. They are more beneficial to soil organisms than a conventional clean-tillage system of molboard plowing and disking.

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Adding manure and compost is a recognized means for improving soil organic matter and humus levels. In their absence perennial is the only crop that can regenerate and increase soil humus. Cool-season grasses build soil organic matter faster than warm-season grasses because they are growing much longer during a given year. When the soil is warm enough for soil organisms to decompose organic matter, cool-season grass is growing.While growing, it is producing organic matter and cycling minerals from the decomposing organic matter in the soil. In other words, there is a net gain of organic matter because the cool-season grass is producing organic matter faster than it is being used up.

With warm-season grasses, organic matter production during the growing season can be slowed during the long dormant season from fall through early spring. During the beginning and end of this dormant period, the soil is still biologically active, yet not grass growth is proceeding. Some net accumulation of organic matter can occur under warm-season grasses.However, in a Texas study, switchgrass (a warm-season grass)grown for four years increased soil carbon content from 1.1% to 1.5% in the top 12 inches of soil.In hot and moist regions, a cropping rotation that includes several years of pasture will be most beneficial.

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Effect of Nitrogen on Organic Matter

Excessive nitrogen applications stimulate increased microbial activity, which in turn speeds organic matter decomposition.The extra nitrogen narrows the ratio of carbon to nitrogen in the soil.Native or uncultivated soils have approximately 12 parts of carbon to each part of nitrogen, or a C : N ratio of 12 : 1. At this ratio, populations of decay bacteria are kept at a stable level, since additional growth in their population is limited by a lack of nitrogen.When large amounts of inorganic nitrogen are added, the C : N ratio is reduced, which allows the populations of decay organisms to explode as they decompose more organic matter with the now abundant nitrogen.

While soil bacteria can efficiently use moderate applications of inorganic nitrogen accompanied by organic amendments (carbon ), excess nitrogen results in decomposition of existing organic matter at a rapid rate. Eventually, soil carbon content may be reduced to a level where the bacterial populations are on a starvation diet. With little carbon available, bacterial populations shrink, and less of the free soil nitrogen absorbed.

Thereafter, applied nitrogen, rather than being cycled through microbial organisms and re-released to plants slowly over time, becomes subject to leaching. This can greatly reduced the efficiency of fertilization and to environmental problems. To minimize the fast decomposition of soil organic matter, carbon should be added with nitrogen. Typical carbon sources – such as green manures, animal manure, and compost –serve – this purpose well.

Amendments containing too high a carbon to nitrogen ratio (25:1 or more) can tip the balance the other way, resulting in nitrogen being tied up in an unavailable form. Soil organisms consume all the nitrogen in an effort to decompose the abundant carbon ; tied up in the soil organisms, nitrogen remains unavailable for plant uptake. As soon as a soil microorganism dies and decomposes, its nitrogen is consumed by another soil organism, until the balance between carbon and nitrogen is achieved again.

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EXPERIMENNT 2.3 Determination of Organic Matter Content of The Soil

Purpose : to determine the organic matter content in the soil sampleApparatus:

Desiccators Tripod Bunsen burner Asbestos mat Fire clay triangle tongs Crucible

Materials : Dried soil sample

Procedure

1. Crucible and lid strongly heated to remove all trace of moisture. The crucible and lid then cooled in the desiccators and the mass (X ) is weighted and recorded.

2. 1/3 of the crucible is filled with the soil sample that has been previously dried in an oven (105 - 110 celsius). The crucible is covered and weighed again. The mass (Y )is recorded.

3. The covered crucible and its contents are then heated until red-hot for approximately 1 hour to burn off all the organic matter. The hot crucible and its contents are then cooled in desiccators after which they weighed. The mass ( Z ) is recorded.

4. This step is repeated until a constant weight is obtained.5. The percentage of organic matter content in the soil sample is calculated as follow :

Y-Z x100 Y-X

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Results

From the weight readings obtained, the percentage of organic matter in soil sample can be calculated as follows :Crucible +cover = 17.11 gCrucible +cover + soil before heating = 24.05 gCrucible +cover + soil after heating = 22.56 gSoil sample used = (24.05 - 17.11 ) g = 6.94 gOrganic matter = ( 24.05 – 22.56 ) g = 1.49 g

Percentage of organic component = Weight of organic matter x100 Weight of soil sample used = 1.49 g x100 6.94 g = 21.47 %

Discussion

1. Dried soil sample is used in order to prevent including the weight of water while measuring the weight of organic matter.

2. Soil sample is dried in oven at the temperature of 101 -110 celsius which is consider as most suitable range of temperature to remove trace of moisture in the soil sample. If the soil sample is dried under 90 celcius of temperature, there will be still containing moisture, but if its dried at 150 celcius, all trace of moisture will be totally remove but it will as well burn off the organic matter contain in the soil sample. This causes the organic matter of soil sample can not be determine by us.

3. Soil sample that used in this experiment required to heat for 1 hour in order to organic matter in soil sample will be completely oxidized by heat provided.

4. To ensure that oxidation of organic matter contains in the soil sample is complete; the experiment should be repeated so that the constant value of the weight of organic matter is obtained.

Precaution Steps

1. During the soil sample is heated in the crucible, the crucible have to be covered by a lid to prevent the transfer of heat to surroundings.

Conclusion

The percentage of organic matter content in the soil sample is 21.47 %

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2.4 Water Content of Soil

Soil Water Definitions

Soil water is classified into three categories : ( 1 ) excess soil water or gravitational water, ( 2 ) available soil water, and ( 3 ) unavailable soil water. See Figure 2.41 for a schematic representation of soil water,

Figure 2.40 Soil Water Levels within Three Soil Types

Excess soil water or gravitational water ( Figure 2.41 ) drains or percolates readily by gravitational force. Since drainage takes time, part of the excess water may be used by plants before it moves out of the root zone.

Available soil water (figure 2.42 ) is retained in the soil by capillary forces and can be extracted by the plant. This soil water is most important for crop production. It is the water held by the soil between field capacity and wilting point. plants can use approximately 50 percent of the available water without stress. When less than 50 percent of available water remains, stress can occur.

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Field capacity is the water content of a soil at a upper limit of the available water range. It is the amount of water remaining in a soil after it has been saturated and allowed to drain for 24 hours.

Permanent wilting point is the lower limit of the available water range. When plants have removed all of the available water from a given soil, they wilt and do not recover. Thus, the water available for plant growth exists between the range of field capacity and wilting point.

Available water capacity is all the water that a soil can possibly hold between field capacity and wilting point.The capacity varies with soil texture.

Unavailable soil water ( Figure 2.43 ) is soil water held so firmly to soil particles by adsorptive soil forces that it can not be extracted by plants. Unavailable water remains when soil is direr than wilting point.

Volumetric water content is the total amount of water that a soil holds at a particular time, It includes the available, unavailable, and gravitational water if present. Volumetric water content is the fraction or percent of water in the total soil volume. Sands, loams, and clay loams reach saturation when volumetric water content is 45 percent, 48 percent, and 52 percent, respectively.

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Figure 2.41 Gravitational Water Figure 2.42 Available Water

Figure 2.43 Unavailable Soil Water

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Soil Water Retention

The soil holds water in two ways : ( 1 ) as a film coating on soil particles, and ( 2 ) in the pore space between particles. When water infiltrates into the soil from rain or irrigation, the pore spaces are nearly filled with water. During and immediately after a rain or irrigation greatest movement of water occurs in the soil. Afterward, water movement continues due to gravity and capillary forces. Capillary forces are also important for retaining water in soil pores.

Figure 2.44 Capillary force is illustrated by how far water rises in tubes of various diameters.

Capillary forces can be illustrated by a group of small capillary tubes with different diameters ( Figure 2.44 ). If the capillary tubes are placed with one end in a pan of water, the water would rise into each tube. The height of the water in each tube would depend on the diameter of the tube. The smaller the tube, the higher the rise. The surface tension of the water itself and the diameter of the tube cause the water to rise. The water must be under negative pressure to rise because this capillary phenomenon can operate in any direction. It is the key to water retention in the soil pores. The pore geometry is much more complex than the simple capillary tubes, but the water is under negative pressure due to the capillary forces.

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Soil Water Tension

Different diameters of capillary tubes illustrate how water is held in soils. The capillary force or tension with which water is held in the soil is most important to plant growth. Smaller pores hold water with more tension ( negative pressure ) than larger pores. Also as films of water around soil separates or aggregates get thinner, water tension increases.As soil dries, the tension of the remaining water increases. Plants can extract water more readily when water tension is small.

Soil water tension measures the force with which water is retained by the soil. Tension is a measure of negative pressure. Commonly tension units are bars which are nearly equivalent to 1 atmosphere ( 14.7 psi ). A plant which is extracting water from a soil at 1/2 bar means it is exerting a negative pressure of about 7 psi. The same plant would exert – 147 psi if the soil were at 10 bars of tension.Table 2.40 illustrates typical soil water tensions for three soil textures.

Sand Loam Silty Clay LoamSoil Water Tension( bars )

Field Capacity 0.1 0.3 0.250 % Available

Water Remaining0.4 1.5 2.0

Wilting Point 15.0 15.0 15.0

Table 2.40 Soil Water Tension for Three Soil Textures.

In unsaturated soil, Soil Water Retension Curves water is under tension and it takes energy to remove it from the soil. The negative pressure to remove water from soil at given water content can be measured. As the water content of a soil decreases from the saturation point, the tension used to hold water increases. In the range of water available for plant growth, not all water is equally available.

The relationship of soil water content and soil water tension is represented in Figure 2.45. Curves like Figure 2.45 are call water retension or soil water characteristic curves. They are different for each soil because of differences in soil textures and structures. At field capacity the soil water is held with a certain tension. For most soils this corresponds to a negative pressure of 0.1 – 0.3 atmospheres.

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Figure 2.45 the relationship of soil water content and soil water tension.

The approximate range of available water content for a loam soil is depicted in Figure 2.45. As the soil dries, a plant will begin to wilt during the day but will recover at night. When the soil water content decreases until the plant cannot extract enough water to recover from its wilted condition, the soil water is at wilting point. This soil water content corresponds to a tension of about 15 bars Loam soil has about 11 percent volumetric water content at wilting. The soil still contains water but it is held too tightly for plant root extraction.

Available Water Capacities

A soil’s water storange characteristics are very important for irrigation management. Since the size and number of pores in soils are directly related to soil texture ( particle sizes ), soil texture is the indicator for the amount of water a soil can hold. Table 2.41 is based on soil texture and can be used to determine the amount of available soil water that a given soil profile will hold. This is its available water capacity.

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Textural Clases

Available Water Capacityin Inches / Food of Depth

Coarse Sands 0.25 – 0.75Fine Sands 0.75 – 1.00Loamy Sands 1.10 – 1.20Sandy Loams 1.25 – 1.40Fine Sandy Loam 1.50 – 2.00Silt Loams 2.00 – 2.50Silty Clay Loams 1.80 – 2.00Silty Clay 1.50 – 1.70Clay 1.20 – 1.50

Table 2.41 Available Water Capacity based on soil texture

Plant available water capacity changes with soil textures. Soil texture often changes with depth because the soil horizons differ. Table 2.42 gives an example for two soils.

Depthfrom surface

( inches )

Available Water Total

Valentine fine sand0 – 6 1.2 0.66 – 24 1.0 1.424 – 60 0.7 2.2

4.2Hasting silt loam

0 – 6 silt loam 2.6 1.36 – 48 silt clay loam 2.2 7.648 – 60 silt loam 2,4 2.4

11.3

Table 2.42 Effect of the soil depth on plant available water capacity

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Application of Soil Water Information

Soil water holding characteristics are important for irrigation system selection, irrigation scheduling, crop selection, and ground water quality. Soil water content in the crop’s active root zone and available water capacity are the key indicators for applying the right amount of irrigation at the right time. This is irrigation scheduling. Whether sprinkler ( center pivot ) or surface ( gravity ) irrigation systems will work on a particular field depends on the soil texture.

Since soil can hold only so much water, excess or gravitation water moves out of the crop root zone toward the groundwater table.Any dissolved nutrients or chemicals move with the water and can eventually end up in ground water.

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EXPERIMENT 2.4 Determination of Water Content of Soil Purpose: to determination the water content in the soil sampleApparatus : - Desiccators - Oven - Thermometer - Petri Dish - Crucible

Materials : - Dried soil sample

Procedure

1. Empty Petri dish is weighed and is mass (a) is recorded2. Soil sample is added to the Petri dish and weighted.Mass (b) is recorded.3. The Petri dish that’s contains the soil sample is placed in the oven under 110 C of

temperature for a hour to get rid of any moisture trace.4. Then the soil sample is removed from oven and cooled in desiccators and weighed

again.The mass (c) is recorded.5. The soil sample is returned to the oven at 110 C for another 1 hour.6. Step 3 and 4 is repeated until a constant weight is obtained.7. The percentage of water content in soil sample is determine and calculated as

follows:

b-c x 100b-a

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Results

>From the weight readings obtained, the percentage of water content in soil sample can be calculated as follows:- Weight of Petri dish (a) =29.39 g Weight of Petri dish + soil before drying (b) = 132.32 g Weight of Petri dish + soil after drying (c) = 116.20 g

Percentage of water content = weight of water content x 100 Weight of soil sample used =(132.32-116.20)g x 100 (132.32-29.39)g =15.66%

Discussion 1. Vaporization takes place when the soil sample dried in the oven.2. Some water content in the soil sample cannot be lost through vaporization; water

content in the hydrated crystalline chemical compound can be removing by drying it in the oven for not less than 1 hour.

3. Soil sample is dried in an oven at temperature 110 C for an hour because this is consider as approximate temperature to eliminate all the water trace in the soil sample including hygroscopic water.

4. Experiment is repeated until constant mass is obtained in order to make sure that the soil sample is completely dried off.

Precaution Steps

1. During the soil sample is heated in the crucible, the crucible have to be covered by a lid to prevent the transfer of heat to the surroundings.

2. A broken-up soil sample is used to provide enough surface area for the vaporization of water.

Conclusion

The percentage of water content in the soil sample is 15.66%

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2.5 Air Content of Soil

Water is soil air?

Atmosphere penetrates into the soil though the pore space and fissures. After rain once excess moisture has drained from the soil, the volume of air-filled pores is known as the air-capacity.

Soil air differs from atmospheric air in that (1) it is saturated with water vapour (near 100% humidity), and (2) carbon dioxide, a by-product of decomposition, is sometime 5-10 times higher. More organic matter in a base-rich soil would favour soil fauna which deplete soil oxygen and increase soil carbon dioxide.

When the pores are saturated with water, fresh oxygen can not diffuse into the soil, creating anaerobic condition. Plant growth is inhibited and chemical reduction may occur in soil (as opposed to oxidation).The by-products of the reduction of nitrates, manganese oxide, sulphate, and iron oxide cause fermentation that produces gases in the soil that are ultimately released to the atmosphere. Such gases in the nitrous oxide (NO2), hydrogen sulphide (H2S), carbon dioxide (CO2), carbon monoxide (CO),and methane (CH4).

It appears that soils play an important role in the sorption of greenhouse gases (‘carbon sink’) as twice as much carbon is found in the soil as in the atmosphere. Disruption of natural soil processes, such as by deforestation and increased cultivation, releases carbon dioxide to the atmosphere. An increase in floodwater farming (e.g rice fields) creates anaerobic condition, released more greenhouse gases in the atmosphere in the form of nitrogen compounds (especially NO2) and methane (CH4).

The movement of gases into and out of the atmosphere takes place by diffusion, defined as the movement of molecules along a gradient. For example, water diffusion occurs from areas of abundance (wet areas) to areas of deficit (dry ones). Gases diffuse along zones of high concentration to areas of low concentration.

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EXPERIMENT 2.5 Determination of Air Content of Soil

Purpose: To determination the air content in the soil sample Apparatus: - Empty milk cane - Measuring cylinder - Puncher

Materials:- soil sample

Procedure :

1. The volume of an empty milk cane is determined by using water and measuring cylinder.

2. Holes are punched by using suitable kind of puncher at the base of the milk cane.

3. The punched milk cane is then pushed into soil to obtain a cane full of undisturbed soil sample

4. Cane is then carefully removed from the soil together with soil sample which occupied the volume of the cane.

5. Then the soil sample from the cane is poured carefully into the large measuring cylinder.

6. 640 cm of water is measured using other measuring cylinder before water is added into the cylinder containing soil sample.

7. This mixture is then vigorously shaken.8. The final volume of the water and soil mixture is then read and recorded.

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Result

From the weight readings obtained, the percentage of air content in soil sample can be calculated as follows:-

Volume of milk cane, V =600cm Volume of the soil sample,(a) =600cm Volume of water used, V =640cm Volume of water and soil sample mixture,V =920cm Volume of air contain in the soil sample, (V+V) = 1240cm Percentage of air content in the soil sample = (V+V)-V x 100 A = (640+640)-920 x 100 600 =53.30%

Discussion

1. The milk cane is pushed into the soil in order to get the exact percentage of air content of the soil sample.

2. Water is used to occupy the soil part that contains air, this will force the soil sample to release air content in it.

3. Holes are made in the surface of the milk cane to let the flow of air in the soil sample going as usual.

Precaution Steps

1. Make sure that the milk cane is pushed into the soil before dig out the soil that the exact percentage of air in the soil sample can be calculated.

Conclusion

The percentage of air content in the soil sample is 53.30%.

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2.6 Soil pH

What is Soil PH ?

An additional important chemical measure is soil ph which refers to the soil’s acidity or alkalinity. This property hinges on the concentration of hydrogen ions in solution. A greater concentration of hydrogen result in a lower ph, meaning greater acidity. Scientists consider pure water, with a ph of 7, neutral.

The ph of a soil will often determine whether certain plants can be grown successfully. Blueberry plants, for example, require acidic soils with a ph of roughly 4 to 4.5.Alfalfa and many grasses, on the other hand, require a neutral or slightly alkaline soil. In agriculture, farmers add limestone to acid soil to neutralize them.

A soil solution occurs when any soluble constituents of soil are dissolved in the soil water. This provides the mechanism by which plants uptake nutrients, as these are held in solution in the soil water.

The hydrogen ions held in solution can be measured using the ph scale. Values above 7.0 are alkaline (basic) which values below 7.0 are acidic. Soils usually have a ph range between 3.0 and 10.0. In humid regions, ph ranges between 5 to 7, while in desert regions, ph ranges between 7 to 9.

Soil ph is an important property of soils as it is a good guide in the diagnosis of fertility problems. Plant nutrients are less available at either extreme of the ph scale, as other elements become available in toxic amounts.

Soil solutions transport soil constituents from one horizon to anther either by solution if the compounds are soluble, or in suspension, such as the clays and silts that are washed down the soil profile.

On horizontal soils, movement of soil solution is vertically downward. However, on slopes, movement of soil solution can also be lateral (to the sides), which helps to produce a sequence of different soils on slopes known as a catena. However, a catena also arises due to effects of gravity, steepness of slope, and land-use history, such that catena also describes a concept useful in the interpretation of soil-landscape relationships in all environments.

In arid environments, movement of soil solution can be upward due to intense evaporation at the very hot surface. Soluble slats will then be precipitated in the upper soil horizons, which cause problems for agriculture in arid areas.

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EXPERIMENT 2.6 Determination of SOIL PH

Purpose: To determine the pH value of soil sampleApparatus:

Test tube Test-tube rack Spatula Pipette

Materials:

Soil sample pH paper

Procedure

1. 1cm of soil sample is measured and added to a test-tube by using spatula.2. Then 1cm of Barium Sulphate is added into the same test-tube which contain soil

sample.3. 10cm of distilled water is then added into that same test-tube.4. Then that test-tube is sealed with rubber.5. The mixture in the sealed test-tube is then shaken vigorously and contents are

allowed to settle for 5 minutes.6. This solution then tested with ph paper.7. With reference to colours chart, the corresponding ph values is read and recorded.

Results

The pH value of the soil sample used is 7.0, which is consider as neutral and suitable for the growth and development for most the plants species.

Discussion .

1. Barium Sulphate is used to ensures flocculation of colloidial clay.

Conclusion

The PH value of soil sample that used in this experiment is 7.0

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The Importance of Soil Organisms

Soil organisms (biota) carry out a wide range of processes that are important for the maintenance of soil health and fertility in both natural and managed agricultural soils. The total number of organisms, the diversity of species and the activity of the soil biota will fluctuate as the soil environment changes. These changes may caused by natural or imposed systems.

An acre of living topsoil approximately 900 pounds of earthworms, 2400 pounds of fungi, 1500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of arthropods and algae, and even small mammals in some cases. Therefore, the soil can be viewed as a living community rather than an inert body. Soil organic matter also contains dead organisms, plant matter and other organic materials in various phases of decomposition. Humus, the dark-coloured organic material in the final stages of decomposition, is relatively stable. Both organic matter and humus serve as reservoirs of plants nutrients, they also help to build soil structure and provide other benefits.

The type of healthy living soil required to support humans now and far into the future will be balanced in nutrients and high in humus, with broad diversity of soil organisms. It will produce healthy plants with minimal weed, disease, and insect pressure. To accomplish this, we need to work will the natural processes and optimize their functions to sustain our farms.

Considering the natural landscape, you might wonder how native prairies and forests function in the absence of tillage and fertilizers. These soils are tilled by soil organisms, not by machinery. They are fertilized too, but the fertility is used again and never leaves the site. Native soils are covered with a layer of plant litter and/ or growing plants throughout the year. Beneath the surface litter, a rich complexity of soil organisms decompose plant residue and dead roots, then release their stored nutrients slowly over time. In fact, topsoil is the most biologically diverse part of the earth. Soil-dwelling organisms release bound-up minerals, converting them into plant-available forms that are then taken up by the plants growing on the site. The organisms recycle nutrients again and again with the death and decay of each new generation of plants.

There are many different types of creatures that live on or in the topsoil. Each has a role to play. These organisms will work for the farmer’s benefit if we simply manage for their survival. Consequently, we may refer to them as soil livestock. While a great variety of organisms contribute to soil fertility, earthworms, arthropods, and the various micro-organisms merit particular attention.

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Figure 3.0 The soil is teeming with organisms that cycle nutrients from soil to plant and back again.

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Earthworms

Earthworm burrows enhance water infiltration and soil aeration. Fields that is ‘tilled’ by earthworm tunnelling can absorb water at a rate 4 to 10 times that of fields lacking worm tunnels. This reduces water runoff, recharges groundwater, and helps store more soil water for dry spells. Vertical earthworm burrows pipe air deeper into the soil, stimulating in high numbers, the tillage provided by their burrows can replace some expensive tillage work done by machinery.

Worms eat dead plant material left on top of the soil and redistribute the organic matter and nutrients throughout the topsoil layer. Nutrient-rich organic compounds line their tunnels allow, which may remain in place for years if not disturbed. During droughts these tunnels allow for deep plant root penetration into subsoil region of higher moisture content. In addition to organic matter, worms also consume soil and soil microbes. The soil clusters they expel from their digestive tracts are known as worm casts or castings. These range from the size of a mustard seed to of a sorghum seed, depending on the size of the worm.

The soluble nutrient content of worm casts is considerably higher than of the original soil (Table 3.0).A good population of earthworms can process 20,000 pounds of topsoil per year-with turnover as high as 200 tons per acre having been reported in some exceptional cases. Earthworms also secrete a plant growth stimulant. Reported increases in plant growth following earthworm activity may be partially attributed to this substance, not just too improved soil quality.

Nutrient Worm casts (Lbs/ac) Soil (Lbs/ac)Carbon 171,000 78,500Nitrogen 10,720 7,000Phosphorus 280 40Potassium 900 140 From Graff. Soil had 4% organic matter.

Table 3.0 Selected nutrient analyses of worm casts compared to those of the surrounding soil.

Earthworms thrive where there is no tillage. Generally, the less tillage are the better and the shallower the tillage the better. Worm numbers can be reduced by as much as 90% by and frequent tillage. Tillage reduces earthworm population by drying the soil, burying the plant residue they feed on and making the soil more likely to freeze. Tillage also destroys vertical worm burrows and can kill cut up the worms themselves. Worms are dormant in the hot part the summer and in the cold of winter.

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Young worms emerge in spring and fall-they are most active when farmers are likely to be tilling the soil. Table 3.01 shows the effect of tillage and cropping practices on earthworm numbers.

Crop Management Worms/foot2Corn Plow 1Corn No-till 2Soybean Plow 6Soybean No-till 14Bluegrass/clover --- 39Dairy pasture --- 33 From Kladivko.

Table 3.01 Effect of crop management on earthworm population

As a rule, earthworm numbers can be increased by reducing eliminating tillage (especially fall tillage), not using a mouldboard plow, reducing residue particle size (using a straw chopper on the combine), adding animal manure and growing green manure crops. It is beneficial to leave as much surface residue as possible year-round. Cropping system that typically have the most earthworms are (in descending order) perennial cool-season grass grazed rotationally, worm-season perennial grass grazed rotationally, and annual croplands using no-till.

Ride-till and strip tillage will generally have more earthworms than clean tillage involving plowing and disking. Col season grass rotationally grazed is highest because it provides an undisturbed (no-tillage) environment plus abundant organic matter from the grass roots and fallen grass litter. Generally speaking, worms want their food on top, and they want to be left alone.

Earthworms prefer a near-neutral soil ph, moist soil condition, and plenty of plant residues on the soil surface. They are sensitive to certain pesticides and some incorporated fertlizers. Carbamate insecticides, including Furadan, Sevin and Temik, are harmful to earthworms, notes worm biologist Clive Edwards of Ohio State University. Some insecticides in the organophosphate family are mildly toxic to earthworms, while synthetic pyrethroids are harmless to them. Most herbicides have little effect on worms expect for the triazines, such as Atrazine, which are moderately toxic. Also, anhydrous ammonia kills earthworms in the injection zone because it dries the soil temporarily increases the ph there. High rates of ammonium-based fertilizers are soil also harmful.

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Arthropods

In addition to earthworms, there are many other species of soil organisms that can be seen by the naked eye. Among them are sowbugs, millipedes, centipedes,slugs, snails and springtails. There are the primary decomposers. Their role is to eat shred the large particles of plant and animal residues.

Some bury residue, bringing it into contact with other soil organisms that further decompose it. Some members of this group prey on smaller soil organisms. The springtail are small insects that eat mostly fungi. Their waste is rich in plant nutrients released after other fungi and bacteria decompose it. Also of interest are dung beetles, which play a valuable in recycling manure and reducing livestock intestinal parasites and flies.

Bacteria

Bacteria are the most numerous type of soil organisms : Every gram of soil contains at least a million of these tint one-celled organisms. There are many different species of bacteria, each with its own role in the soil environment. One of the major benefits bacteria provide for plants is in making nutrients available to them. Some species release nitrogen, sulphur, phosphorus and trace elements from organic matter. Other break down soil mineral, release potassium, phosphorus, magnesium, calcium and iron. Still other species make release plant growth hormones, which stimulate root growth.

Several species of bacteria transform nitrogen from a gas in the air to forms available for plant use and from these forms back to a gas again. A few species of bacteria fix nitrogen in the roots of legumes, while other fix nitrogen independent of plant association. Bacteria are responsible for converting nitrogen from ammonium to nitrate and back again, depending on certain soil condition. Other benefits to plants provided by various species of bacteria include increasing the solubility of nutrients, improving soil structure, fighting root diseases and detoxifying soil.

Fungi

Fungi come in many different species, sizes and shapes in soil. Some species appear as thread-like colonies, while others are one-celled yeasts. Slime molds and mushrooms are also fungi. Many aid plants by breaking down organic matter or by releasing nutrients from soil minerals. Fungi are generally quick to colonize larger pieces of organic matter and begin the decomposition process. Some fungi produce plant hormones, while others produce antibiotics including penicllin. There are even species of fungi that trap harmful plant-parasitic nematodes.

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The mycorrhizae (my-cor-ry’-zee) are fungi that live either on or in plant roots and act to extend the reach of root hairs into the soil. Mycorrhizae increase the uptake of water and nutrients, especially phosphorus. They are particularly important in degraded or less fertile soils. Roots colonized by mycorrhizae are less likely to be penetrated by root-feeding nematodes, since the pest cannot pierce the thick fungal network. Mycorrhizae also produce hormones and antibiotics that enhance root growth and provide disease suppression. The fungi benefit by taking nutrients and carbohydrates from the plant roots they live in.

Actinomycetes

Actinomycetes (ac-tin-o-my’-cetes) are thread-like bacteria that look like fungi. While not as numerous as bacteria, they too perform vital roles in the soil. Like the bacteria, they help decompose organic matter into humus, releasing nutrients. They also produce antibiotics to fight disease of roots. Many of these same antibiotics are used to treat human disease. Actinomycetes are responsible for the sweet, earthy smell noticed whenever a biologically active soil is tilled.

Algae

Many different species of algae live in the upper half-inch of the soil. Unlike most other soil organisms, algae produce their own food thought photosynthesis. They appear as a greenish film on the soil surface following a saturating rain. Algae improve soil structure by producing slimy substance that glue soil together into water-stable aggregates. Some species of algae (the blue-greens) can fix their own nitrogen, some of which is later released to plant roots.

Protozoa

Protozoa are free-living micro-organisms that crawl or swim in the water between soil particles. Many soil protozoa are predatory eating other microbes. One of the most common is an amoeba that eats bacteria. By eating and digesting bacteria, protozoa speed up the cycling of nitrogen from the bacteria, making it more available to plants.

Nematodes

Nematodes are abundant in most soils, and only a few species are harmful to plants. The harmless species eat decaying plant litter, bacteria, fungi, algae, protozoa and other nematodes. Like other soil predators, nematodes speed the rate of nutrient cycling.

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Soil Organisms and Soil Quality

All these organisms- from the tiny bacteria up to the earthworm and insects- interact with one another in a multitude of way in the soil ecosystem. Organisms not directly involved in the other substances they release. Among the substances released by the various microbes are vitamins, amino acids, sugars, antibiotics, gums and waxes.

Roots can also release into the soil various substance that stimulate soil microbes. These substances serve as food for select organism. Some scientists and practitioners theorize that plants use this means to stimulate the specific population of micro-organisms capable of releasing or otherwise producing the kind of nutrition needed by the plants.

Research on life in the soil has determined that there are ideal ratios for certain key organisms in highly productive soils. The Soil Foodweb Lab, located in Oregon, tests soils and makes fertility recommendations that are based on this understanding. Their goal is to alter the makeup of the soil microbial community so it resembles that of a highly fertile and productive soil. There are several different ways to accomplish this goal depending on the situation.

Because we cannot see most of the creatures living in the soil and may not take time to observe the ones we can see, it is easy to forget about them. See Table 3.02 for estimates of typical amounts of various organisms found in fertile soil.

Organisms Pounds of live weight/acreBacteria 1000Actinomycetes 1000Molds 2000Algae 100Protozoa 200Nematodes 50Insects 100Worms 1000Plant roots 2000 From Bollen.

Table 3.02 Weights of soil organisms in the top 7 inches of fertile soil.

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How does Agriculture Influence Soil Biota Activity ?

Any factor that changes the soil environment will impact on the activity and diversity of soil biota. Different soil environments support different types and numbers of biota, example soils under a legume have a higher lever of rhizobia which fix nitrogen for that legume, after a canola crop soil will have a lower level of root disease fungi because of the fungicidal compounds released by the decomposing canola residues.

Agricultural production can result in increased soil carbon inputs from retained crop residues, root residues and increased nutrient levels from fertility. These increase biological activity. Where organic matter declines, biological activity will also decline. Different plant residues will contain varying quantities and availability of carbon (energy), nitrogen ratio C:N ratio, the more readily it is broken down. Consequently, this will also influence the soil biological activity.

Cultivation alters the physical, chemical and biological components of the soil system. No-till/direct-drill system result in significant differences in soil organism activity compared to conventional tillage.

Agricultural inputs, such as fertilisers have been shown to have both a positive and negative effect on soil biological activity. High levels of nitrogen or phosphorus reduce the impact of the symbiotic fixing of these nutrients by Rhizobium (nitrogen) and mycorrhiza (phosphorus), but provide nutrients for non-symbiotic organisms.

Herbicides, insecticides and fungicides may be directly toxic to soil organisms or influence the ‘predator-prey’ interactions. The effect on non-target organisms will depend on whether the product is applied to the bare soil, rate of herbicide decomposition and leaching away from the site of the organisms.

Herbicides applied to stubble cover, as opposed to bare soil, have been shown to persist longer. Continued use of some herbicides, example paraquat, has been shown to significantly depress some groups of micro-organisms. This is usually a short term effect with levels recovering 20 days after herbicide application. Nitrifying bacteria are the most sensitive to herbicide application.

The impact of insecticides on soil biota is more questionable than herbicides, as they are designed to kill fauna. However, the majority of insecticides are applied to plants rather than to the soil.

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Similarly the concentration of fungicides is generally low in the soil. New products, example Impact(?) in furrow change this and more research is required to observe the long term impact on the food-web. The frequency of use will also change the balance of the food-web favoring organisms that are able to live by breaking down the chemical residues.

The challenge for agriculture is to minimize nutrient losses and to maximize internal nutrient cycling. Agricultural practices usually alter more than one soil environmental factor making it difficult to isolate which change is the most significant.

A decline in the total and specific population size is considered detrimental to soil health i.e nutrient status, disease resistance, structure and stability and long term productivity.

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EXPERIMENT 3.1 Extraction of Soil ORGANISMS USING Tullgren Funnel

Purpose: To extract soil organisms using Tullgren FunnelApparatus:

Tullgren Funnel Beaker Hand lens Retort stand with its clamps 60W light source

Materials:

4% formalin solution soil sample

Procedure:

1. Soil sample is collected around the roots part of the plants2. Tullgren Funnel is arranged as shown in the figure 3.10.3. The soil sample is then gently placed on the mesh screen inside the Tullgren Funnel.4. 50ml of 4% formalin solution is then poured into the beaker and the beaker is then

placed directly below the funnel.5. This unit is placed in a place which will not be disturbed. 60W light source which are

placed above the funnel are then turned on.6. Leave the unit for 2 days before the formalin in the beaker is examined for any trace

of organism.7. The soil organism that found in the formalin solution the beaker is then identified

and recorded in the table 3.10.

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Figure 3.10 Tullgren Funnel arrangement

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Result

Type of Organism Common Name Appearances

Phylum arthropodoClass Insecta

Ant

Phylum annelidaClass Oligochaetae

Earthworm(Pheretima sp.)

Phylum arthropodoClass Diplopoda

Milipede(Lulus sp.)

Table 3.10 Types of soil Organism Extracted by using Tullgren Funnel.

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Discussion

1. Not all soil found contain soil organism inside it. Getting soil sample which contain sufficient amount of soil organism to be studied is almost hard to do. Suggested that the soil sample from the fertile land which has excess of humus is suitable to be studied in this experiment. Humus is known as common nutrient of soil organism. Other than that most of the soil organism prefers cold, dark and wet places as their habitat, which means soil sample also can be taken from the land part which is shaded from the direct sun light besides over the plants roots which supply sufficient nutrient for soil organism.

2. The Tullgren Funnel technique is based on the negative responses of the soil organism towards bright light, high temperature and low moisture. These 3 factor forces the soil organism leave the soil sample and they eventually fall into the beaker which contain formalin solution.

3. Broken up soil sample will increases the surface area that exposed to the light and heat. This makes the movement of slow-moving organism a lot easier.

Conclusion

Type of organism that extracted from the soil sample by using Tullgren Funnel are known as macrofauna which is fairly large soil organism including ants, earthworm and millipedes.

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EXPERIMENT 3.2 Extraction of Soil Organism using Bearmann Funnel

Purpose :To extract soil organisms using Bearmann FunnelApparatus: *Beaker *Muslin bag *Rubber tubing *Filter funnel *Light microscope *Retort stand with its clamps *60 W light source *Microscope slides *Dropper *Screw clamps

Materials: *4 % formalin solution *Soil sample *Water

Procedure:

1. Apparatus of the Bearmann funnel is prepared as show in the figure 3.20.2. Rubber tubing is attached to the funnel stem and the end of the tube is blocked

with screw clamps.3. The funnel is supported with the help of retort stand. The height of the clamps

which holds the filter funnel is adjusted in order the tubing hangs free.4. Soil sample which taken from appropriate type of land is wrapped with the

muslin bag and tied up with the length of rope. The rope is determined to be longer than the diameter of the funnel.

5. The clamps at bottom of the tubing are close before the funnel is filled with water.

6. Soil sample that wrapped with muslin bag is then placed inside the filter funnel which is filled with water.

7. More water is add to the funnel until the soil sample that wrapped with muslin bas is just barely submerged.

8. 60 W of light source which placed at the top of the filter funnel is turned on. This unit is left untouched for 12 hour.

9. The clamps at the bottom of the tubing are open in order to drawn small volume of water into a beaker.

10. Using the dropper,a small drop of water is place over the microscope slide and the cover slip is carefully placed at the water drop.

11. These slide then placed under the light microscope, any present of soil organism is observed.Each organism is identified and recorded.

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Figure 3.20 Bearmann Funnel arrangement

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Results

Type Of Organism Common Name

Appearances

Kingdom Animalia Phylum arthropodo (Class Insect)

Larva (Addis fly)

Kingdom Animalia Phylum nematode

Nematode

Kingdom Prototista Phylum rhizophoda

Amoeba sp.

Kingdom Prototista

Phylum ciliophora

Paramecium sp.

Table 3.20 Types of soil Organism Extracted by using Bearmann Funnel

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Discussion

1. The soil sample that wrapped with muslin bag is just barely submerged into the water in the funnel to allow the diffusion of oxygen into the soil sample.2. This technique is based on the fact that some aquatic soil organism such as nematodes and Amoeba sp. Are denser that water.The higher temperature and light intensity in the upper layer when compare to the bases of the funnel, causes these aquatic soil organism to leave the soil sample and gather at the stem of the funnel. When the clamps are opened,these soil organism fall into the beaker containing formalin and can be identified.

Precaution Steps

*The rubber tubing to the funnel is must be tight fit to prevent any leakage.

Conclusion

*Type of organism that extracted from the soil sample by using Bearmann funnel are know as microfauna such as larva,Amoeba sp. Paramecium sp. And nematodes.

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4.0 Community Analysis using the Quadrat Sampling Technique

Quadrats refer to a community patch especially of plants, which has a specified standard sizes,bound by the four sides of a square or a circle. The simplest type of record is a list and the number of individual species bound by the quadrate.In this technique,number of quadrate taken systematically or at random must distribute all over a specific area so that composition of a community can be determined quantitatively.

The quadrat size depends on the sizes and density of the plants that need to be sampled. The quadrats must be large enough so that effective number can be obtained and small enough so that the individual organism can be separate.

For efficient quadrat sampling,suitable quadrat shape is very important.For low plants communities,circular quarates can be used. Other than that,square quadrats which are made from metal or stakes on the ground surrounded by string also can be used. By using quadrate sampling technique density,relative density,coverage,relative coverage,relative density, coverage,relative courage,frequency and relative frequency of plant species can be detemine.

Density refers to the number of individuals of a species per unit area (or volume )of a specific area (habitat).Density can be calculated as follows:

Density = Total number of individuals of a species in all quadrate

Total number of quadrates X area of each quadrate

Relative Density refers to the percentage of density of the species compared to the total density of all species living in the same area.Relative density can be calculated as follow:

RelativeDensity = Density of a species x 100% Total density of all species

Coverage refers to ratio of land area occupied by the vertical projection into air space for each individual species.It is normally stated in percentage units and calculated asfollow :

Coverage = Total base area or area coverage (cm 2 ) of all quadrate x 100 %Total numbers of quadrate sampled X quadrate area

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Relative Coverage refers to the coverage by the species when compared to the total coverage of the entire quadrate by all species. Relative coverage can be calculated asfollow :

Relative Coverage = Coverage by a species x 100 %Total coverage by all species

Frequency which refers to the degree of dispersion of each species in a specific area I stated in percentage units and can be calculated as follow :

Frequency = Number of quadrates containing the species x 100 %Total number of quadrate

Relative Frequency,which refers to the frequency value of the species compared to the total frequency value of all species,is stated in percentage units and calculated as follow:

Relative Frequency = Frequency value of the species x 100 %Total frequency value of all species

The data obtained from quadrats sampling the must be recorded in suitable tables to facilitate our study and analysis.

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SHAPE OF QUADRAT

Quadrat is not natural sampling units, the size and shape of quadrat must always decide.The resulting index of dispersion and the spatial pattern obtained depends on quadrat size and shape.

Chosen the shape of quadrat is important from the aspects of:(a) convenience in laying down the frame of quadrat(b) convenience in setting up the plots.(c) effectiveness of sampling.

Quadrat strictly means a four-sided figurebut in practice mean any sampling unit, whether square, rectangular, circular, hexagonal,oval,or even irregular in outline some of the common shapes of quadrat are:

(a) Square quadrat: The frame are made from metal (iron or aluminium), strips of wood, or rigid plastic which are tied, glued, welded or bolted together in a square. Shape or it can simply be stakes and surrounded by a string on the ground. (This is used within habitats such as scrub areas or woodlands,

where it is not possible to physically lay quadrat frames down because tree trunksand shrubs get in the way.) For aquatic macrophytes a wood or plastic frame will float and also can be used for emergent vegetation on the water surface or sample of floating.

(b) Circular quadrat: This quadrat is used for the place where have low plant community.It is a wooden pole and place in the center. By using-

radius string.(From measuring tape) of various length a circular quadrat of different size can be set up quickly and easily.

(c) Rectangular quadrat: This quadrat can enables a ore effective and also can accurate analysis of the composition at a community if compared to the

usage of same number of square quadrats which are having the same size as the rectangular quadrat.

(d) Point quadrat: The uses of a point frame are to obtain the point samples for estimate cover and it is a device. Set up the frame over the vegetation

and lowered down the needles through the plant canopy. A “hit” is recorded with the species name every time when the point of the needle touches the plant. Before the needles eventually touch the round surface, it can touch several plants. Point sampling method is a method that only can give an accurate estimate of absolute cover of each species in multi-stratose vegetation and hence an estimate of total leaf area species. All other method gives relative percentage cover. It is however, a very time consuming method.

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(c) Rectangular quadrat

Figure 4.10 Shape of Quadrates

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EXPERIMENT 4.1 Quadrate Sampling Techniques

Purpose: To determine the percentage of the relative species cover,relative species density And relative species frequency in a habitat.

Apparatus: Quadrate measuring 1 m2

Preparation

1. It would be waste of time and energy for each group to conduct the quadrat sampling technique in ten different locations. 2. Therefore,our class is divided into ten groups so that we can out quadrat sampling technique in ten different locations at same time.

Procedure

1. Each of the groups has to make a square quadrat. 2. Optionally,a sturdier quadrat can be made using four pieces of PVC pipe and four

elbow joints to connect them. 3. Then,a thread on the quadrat for ever 0.1 m is tide. 4. A location is randomly chosen to place the quadrat within the area of school. 5. Quadrat size is determined so that more eight species of plants can be studied. 6. Quadrate in the same measuring are prepared to be used in the various determined

location.7. The overall species of plants in every quadrate is calculated and written in an

appropriate table to estimate the density of plants species.8. The number of quadrat in which a species occur is calculated to determine the

frequency of the plants species. 9. The percentage of relative density and relative coverage is also calculated.

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Analysis

Student’s name : Muhamad, Chin Tat, Chia Meng, Tze Tze and Yen ShengHabitat : FieldLocation : SchoolType of Plants : GrassQuadrat Size : 1 m2

Date : 14th December 2006

NO Name of plant species

Presence of plant species in quadrat.(put a tick (√) if present)

Number of quadrat with plant species,

n

Percentage Frequency,

[n/10×100%]

Percentage of Relative frequency

(%)1 2 3 4 5 6 7 8 9 10

1 Rumput Kerbau (Paspalum

conjugatum)

√ 1 10 3.6

2 Fimbristylis piphylla /Common

fimbristylis

√ √ √ 3 30 10.7

3 Cyperus zollinger (zollinger’s

cyperus)

√ √ √ √ √ √ √ 7 70 25.0

4 Pick-A-Back (Phyllanthus sp)

√ √ √ √ √ 5 50 17.6

5 Echinochloa colonum

√ √ 2 20 7.1

6 Dactyloctenium aegyptium

√ 1 10 3.6

7 Cyperus brevifolius

√ √ 2 20 7.1

8 Sporobolus indius √ 1 10 3.6

9 Eragrostis malayana stapt

√ 1 10 3.6

10 Crytococoum oxyphllum

√ √ √ √ √ 5 50 17.9

TABLE 4.10: Measurement of frequency of each plant species in quadrat sampling.

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NO Name of plant species

Number of individuals of plant species in quadrat Total number of individuals

of plant species in

10 quadrats,N

Density[N/10×1]

m-2

Percentage of Relative Density (%)1 2 3 4 5 6 7 8 9 10

1 Rumput Kerbau (Paspalum

conjugatum)

23 - - - - - - - - - 23 2.3 5.5

2 Fimbristylis piphylla

/Common fimbristylis

18 32 17 - - - - - - - 67 6.7 16.0

3 Cyperus zollinger (zollinger’s

cyperus)

1 9 - 21 15 19 18 - 1 - 84 8.4 20.1

4 Pick-A-Back (Phyllanthus sp)

11 - - 6 - - 23 - 9 2 51 5.1 0.1

5 Echinochloa colonum

- - 1 - - - - - - 3 4 0.4 1.0

6 Dactyloctenium aegyptium

- - 5 - - - - - - - 5 0.5 1.2

7 Cyperus brevifolius

- - 2 - - - - 7 - - 9 0.9 2.2

8 Sporobolus indius

- - 30 - - - - - - - 30 3.0 7.2

9 Eragrostis malayana stapt

- - - - 7 - - - - - 7 0.7 1.7

10 Crytococoum oxyphllum

- 40 - - 35 - - 31 12 20 138 13.8 33.0

TABLE 4.11: Measurement of density of each plant species in quadrat sampling.

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Students’names: Muhamad, Chia Meng, Chin Tat, Tze tze, Yen ShenHabitat: GrasslandLocation / Place : SMK Telok DatokType of plant: GrassQuadrat size: 1m2 Total number of quadrat: 10Date : 2 November 2006

NO

Name of plant species

Species cover (aerial) in quadrat/m2 Total species

cover for 10

quadrats,a (m2)

Percentagecover, [a/10×) ×100]%

Percentage of

Relativecover(%)

1 2 3 4 5 6 7 8 9 10

1 Rumput Kerbau (Paspalum

conjugatum)

0.07 - - - - - - - - - 0.070 0.70 2.82

2 Fimbristylis piphylla

/Common fimbristylis

0.04 0.08 0.08 - - - - - - - 0.200 2.00 8.05

3 Cyperus zollinger (zollinger’s

cyperus)

0.06 0.10 - 0.17 0.15 0.26 0.04 - 3.50 ×

10-2

- 0.815 8.15 32.81

4 Pick-A-Back (Phyllanthus sp)

0.05 - - 0.09 - - 4.50 ×

10-2

- 0.06 0.07 0.315 3.15 12.68

5 Echinochloa colonum

- - 7.40×

10-2

- - - - - - 0.26 0.334 3.34 13.45

6 Dactyloctenium aegyptium

- - 6.50×

10-2

- - - - - - - 0.065 0.65 2.62

7 Cyperus brevifolius

- - 0.05 - - - - 0.13 - - 0.180 1.80 7.25

8 Sporobolus indius - - 6.50×

10-2

- - - - - - - 0.065 0.65 2.62

9 Eragrostis malayana stapt

- - - - 0.14 - - - - - 0.140 1.40 5.64

10 Crytococoum oxyphllum

- 4.50×

10-2

- - 0.04 - - 0.10 0.07 4.50×

10-2

0.300 3.00 12.08

TABLE 4.12: Measurement of each species cover in quadrat sampling.

Discussion

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1. The plants which is not exactly in the quadrat frame (not fully inside quadrat frame) can be consider as :

Included if the plants species has its roots spreading more than half inside the quadrat (can be considered as one individual plants).

Excluded if the plants species has its roots spreading more than half out of the quadrat.

2. But for certain types of plants species the definition of the arbitrary can be varies depends on the plants species.

Conclusion

From the analysis, Axonopus compressus is determined to have the highest density and relative density with 6.2 per m2 and 15.94% while Bruchiaria pospaloides has the lowest density with 3.0 per m2 and lowest relative density with 7.71%.

From the data in the table 4.11,we can estimate that Cyperus radians have the highest frequency which is 70% and 13.73%.Plant species which have lowest frequency and relative frequency is Fimbristylis Globulosa which is 40% and 7.84%.

Plants species with highest relative coverage is Axonopus Compressus with 6.2% while Plants species with relative coverage 3.0% and also considered has the lowest relative Coverage is Bruchiaria Pospaloides.

4.2 Community analysis using the transect technique.

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Transect refer to a line that cuts across a community in which the plant types are represent By suitable symbols. Usually used in areas where there are many types of plants whish quarats sampling technique can not be used. Transect forms uniform sequential zones representing different communities.

The division into zones is usually related to the uniform variation in physical factors in that habitat along the that are perpendicular to the zones.Transect can show the progressive invasion of plants into the community from one side without causing any change in that habitat.

An advantage of transect charts is that they can show a range of specific plants. Charting these transect at suitable time intervals,ensure us to detect any progressive change plant area include composition, extrapolation,individual occurrence of different species.Transect can be divided to three types which is :

1.Line transects *Simplest and easiest to use. *Can be prepared by placing a measuring tape (15-30 m)along a desired line and marking the location of individual plants that touch one or both side of the tape. *These plants ate than named and given suitable symbol on one or both sides of the line drawn on a scaled paper.

2.Strip transect *A strip of uniform width,(e g: 1m)marked by the parallel measuring tapes that run across the area under study. *For large tree,strip with 5m width will needed. *Strip transect have advantage seen in both transect techniques and are specifically created to illustrate detailed changes of plants along the transect lines.

3.Profile transect *Profile or plants draw according to a specific scale to show the relative height of different plants measured from ground level. *This is based on line transect and is complementary to strip transect.

*Strip transect illustrate distribute in two dimensions. *Can prepared by running a measuring tape along the length of a line transect and the measuring the heights from the ground surface must also be shown.

EXPERIMENT 4.2 Sampling Technique using Line Transect

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Purpose: To determine the frequency,relative frequency,coverage and relative Coverage of the plants species.Apparatus: Rope (15.30 meters )

Procedure

1. A base line along the border of the area under investigation is determined. 2. A series of points along this base line either randomly or systematically is chosen. 3. These points are used as the starting point for this transect line to run across the area

being investigated. 4. Only the plans which toughes the line as seen vertically above or below the tansect

line is recorded. 5. 10 lines are placed randomly in the area to provide enough samples to investigate the

community. 6. Percentage cover,relative percentage and frequency of each plant species is then

calculated.

Analysis

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Student name :Date : 14th December 2006 Habitat : FieldLocation: SMK Telok DatokType of plants : GrassDistance of each Interval : 1mTotal number of Internal : 10Total length of Line Transect : 10 m

NO Name of plant species

Presence of plant species in quadrat.(put a tick (√) if present)

Number of quadrat with plant species,

n

Percentage Frequency,

[n/10×100%]

Percentage of Relative frequency

(%)1 2 3 4 5 6 7 8 9 10

1 Rumput Kerbau (Paspalum

conjugatum)

√ 1 10 3.6

2 Fimbristylis piphylla /Common

fimbristylis

√ √ √ 3 30 10.7

3 Cyperus zollinger (zollinger’s

cyperus)

√ √ √ √ √ √ √ 7 70 25.0

4 Pick-A-Back (Phyllanthus sp)

√ √ √ √ √ 5 50 17.6

5 Echinochloa colonum

√ √ 2 20 7.1

6 Dactyloctenium aegyptium

√ 1 10 3.6

7 Cyperus brevifolius

√ √ 2 20 7.1

8 Sporobolus indius √ 1 10 3.6

9 Eragrostis malayana stapt

√ 1 10 3.6

10 Crytococoum oxyphllum

√ √ √ √ √ 5 50 17.9

TABLE 4.13: Measurement of frequency of each plant species in quadrat sampling.

Name of Species cover (aerial) in quadrat/m2 Percentage

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NO

plant species Total species

cover for 10

quadrats,a (m2)

cover, [a/10×) ×100]%

Percentage of

Relativecover(%)

1 2 3 4 5 6 7 8 9 10

1 Rumput Kerbau (Paspalum

conjugatum)

0.07 - - - - - - - - - 0.070 0.70 2.82

2 Fimbristylis piphylla

/Common fimbristylis

0.04 0.08 0.08 - - - - - - - 0.200 2.00 8.05

3 Cyperus zollinger (zollinger’s

cyperus)

0.06 0.10 - 0.17 0.15 0.26 0.04 - 3.50 ×

10-2

- 0.815 8.15 32.81

4 Pick-A-Back (Phyllanthus sp)

0.05 - - 0.09 - - 4.50 ×

10-2

- 0.06 0.07 0.315 3.15 12.68

5 Echinochloa colonum

- - 7.40×

10-2

- - - - - - 0.26 0.334 3.34 13.45

6 Dactyloctenium aegyptium

- - 6.50×

10-2

- - - - - - - 0.065 0.65 2.62

7 Cyperus brevifolius

- - 0.05 - - - - 0.13 - - 0.180 1.80 7.25

8 Sporobolus indius - - 6.50×

10-2

- - - - - - - 0.065 0.65 2.62

9 Eragrostis malayana stapt

- - - - 0.14 - - - - - 0.140 1.40 5.64

10 Crytococoum oxyphllum

- 4.50×

10-2

- - 0.04 - - 0.10 0.07 4.50×

10-2

0.300 3.00 12.08

TABLE 4.14: Measurement of each species cover in quadrat sampling.

Conculsion

The plant species which have the highest frequency is identified as Cyperus aromaticus.The plant species which have the lowest frequency is identified as Cleome icosandra.While,the plant species with the highest percentage of coverage is Cyperus aromaticus.And the plant species with lowest percentage of coverage is Eleusine indica.

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Conclusion

Soil management involves stewardship of the soil herd. The primary factors affecting organic matter content, build-up, and decomposition rate in soils are oxygen content, nitrogen content, moisture content, temperature, and the addition and removal of organic materials. All these factors work together all the time. Any one can limit the others. Theseare the factor that affect the health and reproductive rate of organic matter decomposerorganisms. Managers need to be aware of these factors when making decisions about theirsoils. Let’s take them one at a time.

Increasing oxygen speeds decomposition of organic matter. Tillage is the primary wayExtra oxygen enters the soil. Texture also plays a role, with sandy soils having more aerationthat heavy clay soils. Nitrogen content is influenced by fertilizer additions. Excess nitrogen,with out the addition of carbon, speeds the decomposition of the organic matter. Moisturecontent affects decomposition rates.

Soil microbial populations are most active over cycles of wetting and drying. Their populations increase following wetting, as the soil dries out. After the soil becomes dry,their activity diminishes. Just like humans, soil organisms are profoundly affected by temperature. Their activity is highest within a band of optimum temperature, above and below which their activity diminished.

Adding organic matter provides more food for microbes. To achieve an increase of soilorganic matter, additions must be higher than removals. Over a given year, under averageconditions, 60 to 70 percent of the carbon contained in organic residues added to soil is lost as carbon dioxide. Five to ten percent is assimilated into the organisms that decomposer the organic residues, and the rest becomes ‘new’ humus.

It takes decades for new humus to develop into stable humus, which imparts the nutrient-Holding characteristic humus is know for. The end result of adding a ton of residue would be 400 to 700 pounds of new humus. One percent organic matter weighs 20,000 pounds per acre.A 7-inch depth of topsoil over an are weighs 2 million pounds. Building organic matter is a slow process.

It is more feasible to stabilize and maintain he humus present, before it is lost, than to tryto rebuild it. The value of humus is not fully realized until it is severely depleted. If your soils are high in humus now, work hard to preserve what you have. The formation of new humus is essential to maintaining old humus, and the decomposition of raw organic matter has, any benefits of its own.

Increased aeration caused by tillage coupled with the absence of organic carbon in fertilizer materials has caused more than a 50 %decline in native humus levels an many U.S farms.Appropriate mineral nutrition needs to be present for soil organisms and plants to prosper. Adequate levels of calcium, magnesium, potassium, phosphorus, sodium, and the trace elements should be present, but no in excess.

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The base saturation theory of soil management helps guide decision-making toward achieving optimum levels of these nutrients in the soil. Several books have been written on balancing soil mineral levels, and several consulting firms provide soil analysis and fertility recommendation services based on this theory.

Commercial fertilizers have their place in sustainable agriculture. Some appear harmless to soil livestock and provide nutrients at times of high nutrient demand from crops. Anhyrousammonia and potassium chloride cause problems, however. As noted above, anhydrous kills soil organisms in the injection zone.

Bacteria and Actinomycetes recover within a few weeks, but fungi take longer. The increase in bacteria, fed by highly available nitrogen from the anhydrous, speeds the decomposition of organic matter. Potassium chloride has a high salt index, and some plants and soil organisms are sensitive to chloride.

Topsoil is the farmer’s capital. Sustaining agriculture means sustaining the soil. Maintainingground cover in the form of cover crops, mulch, or crop residue for as much of the annual season as possible achieves the goal of sustaining the soil resource. Any time the soil is tilled and left bare it is susceptible to erosion.

Even small amounts of soil erosion are harmful over time. It is not easy to see the effects of erosion over a human lifetime; therefore, erosion may go unnoticed. Tillage for production of annual crops not created most of the erosion associated with agriculture. Perennial grain crops not requiring tillage provide a promising alternative for drastically improving the sustainabilityof future grain production.

Understanding soil water holding capacity and the factors affecting the plant available soil water are necessary for good irrigation management. Information is readily available from Cooperative Extension and the Soil Conservation Service to help growers assess the conditions specific to their own fields and crops.

Several different techniques are available which can be used to effectively monitor or directly measure soil water content. Some are extremely simple and are well worth the investment of time and labor. Many irrigation scheduling consultants are using these differentmethods.

The cost of keeping track of the soil water on your own or by using a service can be paid back through the benefits of effective water management. Included among these benefits are energy saving, water savings, water quality improvement, and quite often improved crop quality and yields.

Successful implementation of any of the methods evaluated requires careful attention installation, operation, and maintenance requirement discussed. Soil type and irrigation regime are important parameters affecting the choice of a method or technique which will yield the best results.

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A routine sampling schedule should be implement to obtain the most information from any these methods. The difference in soil water content at a given location from one sampling time to the next often provides more information than random space and time measurements. Soil water should be measured or monitored in at least two depths in the expected crop root zone at several locations in a field to obtain a field average. Sub area within fields having different soil textures or other characteristics should also be monitored.

Soil faces many threats throughout the world. Deforestation, overgrazing by livestock and agricultural practices that fail to conserve soil are three main cause of accelerated soil loss. Other acts of human carelessness also damage soil. These include pollution from agriculture pesticides, chemical spills, liquid and soil wastes and acidification from the fall of acid rain.

Loss of green spaces, such as grassland and forested areas, in favor of impermeable surfaces, such as pavement, buildings, and developed land, reduces the amount of soil and increase pressure an what soil remains. Soil is also compact by heavy machinery and off-road vehicles. Compaction rearranges soil particles, increasing the density of the soil and reducing porosity.Crusts form on compacted soils, preventing water movement into the soil increasing runoff erosion.

With the world’s population now numbering upwards of 6 billion people-a figure that may rise to 10 billion or more within three decades –humans will depend more than ever on soil for the growth of the food crops. Yet the rapidly increasing population, the intensity of agriculture, And the replacement of soil with concrete and buildings all reduce the capacity of the soil to fulfill this need.

As a result of an increased awareness of soil’s importance may changes are being made to protect soil. Recent interest in soil conservation holds the promise that humanity will take better care of this precious resource.

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Summary of Sustainable Soil Management Principles

Soil livestock cycle nutrients and provide many other benefits.Organic matter is the food for the soil livestock herd.The soil should be covered to protect it form erosion and temperature extremes.Tillage speeds the decomposition of organic matter.Excess nitrogen speeds the decomposition of organic matter; insufficient nitrogen slows down organic matter decomposition and starves plants.Moldboard plowing speeds the decomposition of organic matter, destroys earthworm habitat, and increase erosion.To build soil organic matter, the production or addition of organic matter must exceed the decomposition of organic matter.Soil fertility levels need to be within acceptable ranges before a soil-building program is begun.

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