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AHS Agriculture
What are the basic needs of plants and various factors that make up their environment?
What factors have the greatest impact on plants?
Factors that have greatest effect on plants are:
Water, nutrition, medium, temperature, light, humidity, insects and diseases
70-90% of fresh weight & major component of green plants.
Medium for biochemical rxns
Transports nutrients & manufactured food
Allows sunlight to penetrate leaves & green stems to reach chlorophyll & power production of food
Vapor cools plant
Stress plantsMore susceptible to disease & insect attacks
Slow process of photosynthesis
16 elements from soil of fertilizer
Nitrogen, phosphorus & potassium needed most often
Growth greatly influenced by heat
Plants unable to maintain cells at uniform temp.
Heat reproduction parts when ready for fertilization
Cool leaves by transpiration (not constant temp)
Roots less affected – soil
Select plants adapted to area
Some plants require # of days at cold temp to flower (impatiens)
Growth increases as temp increases up to 86*F
Above 86*,slows or stops90*-100* severely damage
Reduced growthCan result in death of plants
Cold-hardy plants can die if sudden drop in temp also
More light= grow & flower better
Too much direct light= damage to shade plants
Spring longer days= growing & flowering
Fall shorter days = perennials, shrubs & trees hardening off & preparing for dormancy & cold temps
Why is soil important?
Soil or soil substitute plants are grown in
Casualty of American agricultural revolution- loss of native soil fungi
Allow plants to grow w/ less water, fewer added nutrients, & fewer pesticides
Can now control plant diseases through use of compost & mulch
Also improves drainage
Sand, silt, clay, organic matter, living organisms & pore spaces that hold water & air
Classified on % of sand, silt & clay
Sand larger then silt, clay smallest
Clay important to hold water & nutrients for plant
• topsoil – layer plowed/tilled, contains most organic matter• Subsoil- oxygen available, roots expand here• Soil bedrock/lower subsoil- roots expand until rock, hard clay or water prevents
50% solid material (minerals, organic material)
50% pore space Amount of moisture held depends on soil type
Silt & clay make up less then 20% of material
Drain wellLittle capacity to hold moisture & plant food
At least 30% clay Heavy soilPoor drainage & aeration capabilities
Holds fertilizer, plant food & water well
Most desirable Mixture of equal parts of sand, silt & clay
Answer the questions using the texture triangle to determine the type of soil
What are the varieties of medium?
Drainage & aeration- add organic matter to soil (aggregation)
Lime & gypsum (calcium sulfate)
Raising bedsDitches
Moisture retention- organic matter
Peat moss- 15x its weight Animal manure, green manure, peat moss, sawdust- good organic matter
Yellow or pale leaves = nitrogen deficiency
Purple under leaf= phosphorus deficiency
Nematodes – tiny animalsInsectsCrop rotation & compost to control
Chemicals as last resort
Mix uniformSterileLighter in weightGood moisture retention & drainage
Blown over bc lightMinor plant food elements missing (iron, sulfur, zinc & calcium)
From mixes to soil- hesitate to extend roots
Perlite- gray-white material of volcanic origin. To improve aeration
Peat Moss- partially decomposed vegetation preserved under water
High moisture-holding capacity, 1% nitrogen, low in phosphorus & potassium
• Sphagnum moss- dehydrated remains of acid bog plants in shredded form for seeds• Sterile, lightweight, controls disease well, excellent water-holding capacity• acid
Vermiculite- light, expanded material with neutral pH
High moisture-holding capacity
Limestone- calcium carbonate (CaCO3) raise pH
Tree Bark- pine or oak trees Slow-release fertilizers- plant food gradually made available
May contain 2 or more of above ingredients
Different plants have different requirements
May
How can we ensure proper fertilization?
Most important plant food element
Plant food must be dissolvable in water
Major elementsSecondary nutrientsMinor nutrients
Show % of or lbs per hundred weight of 3 major elements in large #’s on bag or container
5-10-55% nitrogen10% phosphorus5% potassium Other 80% filler material to help spread plant food evenly
Most noticeable effect on plantsEncourages vegetative growthDark green leaves Soft, tender growth, good quality for crops, better tasting
Too much: Lowers resistance to diseaseWeaken stemLower quality of fruitsDelay maturity/damage to plants
Lost by leaching (washing out)
Not held by soil particlesLegumes (beans, peas) manufacture own nitrogen
Held tightly by soil Encourages plant cell division
Flowers & seedsHastens maturity, offsetting quick growth from nitrogen
Encourages root growthMakes potassium more easily available
Increases resistance to disease
Improves quality of grain, root & fruit crops
Can dry out roots by pulling water from roots
Insufficient- purple coloring, reduced fruit, flower & seed production, plant disease, poor quality fruits
Increases resistance to diseaseEncourages strong, healthy roots
Essential for starch formationDevelopment of chlorophyllEncourages use of carbon dioxide
Deficiency as yellowing on edge of leaves
Affects soil acidityAvailability of plant food elements
Pg. 45 pH scaleBest growth 5.6-7
Sulfur, iron sulfate or aluminum sulfate used
Flushing with low salt irrigation also works
Lime to raise pHCan also release phosphorus when too acid
Decreases aluminum & iron Activates soil organisms & encourages release of plant food
Do not lime blueberries, azaleas, & rhododendron
May cause iron deficiency if pH above 6
D
What does a plant need aboveground to survive?
TemperatureLightHumidityPlant DiseasesInsectsGases/Particles
One of strongest affectsSome grow in cooler tempsSome prefer hot tempsNear & below freezing stops plant growth
86* good temp, above plant growth slows
Must be present to produce food
Too much can destroy plantSome plants only bloom when days shorter (chrysanthemum)
Photoperiodism – response to different periods of day & night in terms of growth
Grow towards light Flavanoids- natural sun blockers in leaves
Enzymes to repair leaf damage from UV lgiht
Most not affected 40-80% humidity best High humidity will spread fungus
Relative humidity- amount of moisture in air as compared with the % of moisture that the air could hold at same temp if completely saturated
Reduces productionStem injury may girdle (circle) or clog up a stem & kill plant
Prevent- varieties resistant to diseases and/or insects, crop rotation or chemical sprays
Carbon Dioxide (CO2) vitalSome add to greenhouseDamage: sulfur dioxide (coal furnaces) Carbon monoxide (cars)
Consider fumes
Plant Heat-Zone Map (AHS) Plant Hardiness Zone Map (USDA)
Using both, #’s set up to indicate where plants grow best
First 2= cold hardiness 1st- coldest zone, 2nd- least cold zone
Second set= heat tolerance & requirement. 1st- hottest zone, 2nd- lowest heat zone
EX: Cornus florida, East Coast dogwood (5-8, 8-3)
Other factors will affect plant growth also
Carbon