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