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 plants More 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 stops 90*-100* severely damage
Reduced growth Can 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 well Little capacity to hold moisture & plant food
At least 30% clay Heavy soil Poor 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 beds Ditches
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 animals Insects Crop rotation & compost to control Chemicals as last resort
Mix uniform Sterile Lighter in weight Good moisture retention & drainage
Blown over bc light Minor 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 elements Secondary nutrients Minor nutrients
Show % of or lbs per hundred weight of 3 major elements in large #’s on bag or container
5% nitrogen 10% phosphorus 5% potassium Other 80% filler material to help spread plant food evenly
Most noticeable effect on plants Encourages vegetative growth Dark green leaves Soft, tender growth, good quality for crops, better tasting
Too much: Lowers resistance to disease Weaken stem Lower quality of fruits Delay maturity/damage to plants
Lost by leaching (washing out) Not held by soil particles Legumes (beans, peas) manufacture own nitrogen
Held tightly by soil Encourages plant cell division Flowers & seeds Hastens maturity, offsetting quick growth from nitrogen
Encourages root growth Makes 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 disease Encourages strong, healthy roots Essential for starch formation Development of chlorophyll Encourages use of carbon dioxide
Deficiency as yellowing on edge of leaves
Affects soil acidity Availability of plant food elements
Pg. 45 pH scale Best growth 5.6-7
Sulfur, iron sulfate or aluminum sulfate used Flushing with low salt irrigation also works
Lime to raise pH Can 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
DD
Lesson Essential Question What does a plant need aboveground to survive?
Factors Temperature Light Humidity Plant Diseases Insects Gases/Particles
Temperature One of strongest affects Some grow in cooler temps Some prefer hot temps Near & below freezing stops plant growth 86* good temp, above plant growth slows
Light Must be present to produce food Too much can destroy plant Some plants only bloom when days shorter (chrysanthemum)
Photoperiodism – response to different periods of day & night in terms of growth
Light Grow towards light Flavanoids- natural sun blockers in leaves Enzymes to repair leaf damage from UV lgiht
Humidity Most not affected 40-80% humidity best High humidity will spread fungus
Humidity Relative humidity- amount of moisture in air as compared with the % of moisture that the air could hold at same temp if completely saturated
Plant Diseases & insects Reduces production Stem injury may girdle (circle) or clog up a stem & kill plant Prevent- varieties resistant to diseases and/or insects, crop rotation or chemical sprays
Gases & air particles Carbon Dioxide (CO2) vital Some add to greenhouse Damage: sulfur dioxide (coal furnaces) Carbon monoxide (cars) Consider fumes
Adaptability of plants Plant Heat-Zone Map (AHS) Plant Hardiness Zone Map (USDA) Using both, #’s set up to indicate where plants grow best
#’s First 2= cold hardiness 1 st - coldest zone, 2 nd - least cold zone Second set= heat tolerance & requirement. 1 st - hottest zone, 2 nd - lowest heat zone
#’s EX: Cornus florida, East Coast dogwood (5-8, 8-3) Other factors will affect plant growth also
Activity Carbon