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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 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 subsoilroots 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 Insects Crop – tiny animals 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 soilhesitate 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 waterholding 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 fertilizersplant 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 5-10-5 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 D What does a plant need aboveground to survive? Temperature Light Humidity Plant Diseases Insects Gases/Particles 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 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 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 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 Carbon Dioxide (CO2) vital Some add to greenhouse Damage: 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 1stcoldest zone, 2nd- least cold zone Second set= heat tolerance & st requirement. 1 - hottest zone, 2nd- lowest heat zone EX: Cornus florida, East Coast dogwood (5-8, 8-3) Other factors will affect plant growth also Carbon