Transcript File
20 ESSENTIAL NUTRIENTS Different chemical elements have been identified in plants. Only 16 chemical elements are essential to plant growth and development. Non-Mineral essential nutrients Carbon Hydrogen Oxygen Hydrogen and Oxygen are supplied to plants from carbon dioxide and water through photosynthesis ELEMENT-A simple form of matter that cannot decompose by ordinary chemical means. FERTILIZER- product added to growing material to supply essential macro and micro nutrients. Nitrogen-General Facts One of the most abundant and mobile nutrients Part of every plant cell Soils may contain as much as 5,000 lbs of nitrogen per acre. The air we breathe contains 37,000 tons (78% by weight) over each acre Origin for ALL nitrogen sources Part of chlorophyll-gives the green color Loss of nitrogen results in loss of color-turns yellow Lack of nitrogen causes spindly, weak stems and growth is slowed. Production of nitrogen starts with ammonia This is a gas Combo of atmospheric nitrogen and hydrogen from natural gas and/or fossil fuels. Can be applied directly as a gas or further processed into a liquid or solid fertilizer. Common Sources of Nitrogen Urea Ammonium Nitrate Nitrogen Solutions Nitrogen and the Environment Nitrification Changes to Nitrate—NO3 Decomposed organic materials or inorganic fertilizers are converted to N03 NO3 can get trapped into clay particles of soil Bacteria aids in nitrification Nitrate is available for plant use Nitrate can also be tied up and not available to the plant. Can be as much as 50% Leaching-When water passes through the soil profile and removes chemical compounds or nutrients in solution from soil. Nitrate nitrogen is the form most subject to leaching Nitrates are only bound loosely to the clay particles in soil so they move easily with water. Ammonium binds tightly and does not leach Leaching during growing season and in fine to medium soil texture is minimal-less then 5% Leaching is more likely in course soils Erosion-the removal of soil material by wind or water moving over the land. Run-off water Sediment loss Denitrification Only happens when soil is fully saturated or flooded No oxygen in the soil pores Bacteria converts nitrate to elemental N2-this is a gas 15-30% loss during heavy water situations Volatilization Happens under warm and moist conditions. Urea is converted to ammonium carbonate Ammonium carbonate is converted to ammonia gas Ammonia gas is then released to the atmosphere Happens most commonly when urea (usually in an organic form)is applied to a warm moist surface. If the urea is NOT incorporated into the ground shortly after application and is allowed to dry on the surface-can be 10-30% loss of nitrogen into the atmosphere. Nitrogen Cycle In order to be used by the plant-nitrogen must be plucked from the atmosphere. Nitrogen goes through several changes in the soil before returning to elemental form The cycle is atmospheric nitrogen to usable nitrogen and back to elemental nitrogen Nitrogen Fixation-the process by which elemental nitrogen is removed from the atmosphere by soil bacteria called rhizobia. Bacteria lives on roots of legumes. (Alfalfa, clover, peas, beans) Produce their own nitrogen and do not usually need other sources Organic Matter (Humus) As plants die they decompose (break down) into soil organic matter. The rate of decomposition and the amount of nitrogen released into the soil is determined by the carbon:nitrogen ratio With ratios of about 25:1or less, organic nitrogen is quickly converted to usable nitrates. Mineralization happens most is legumes, animal manures and municipal sludges. If greater the 25:1 ratio then nitrogen is tied up and actually take nitrogen from soil during a slow decompostion. Materials such as straw, sawdust and bark are very high in carbon and break down slowly and may actually cause soil to be deficient in nitrogen. Organic matter that has completely decomposed and is stable with the surrounding soil environment is called humus with a C:N ratio of 12:1 Humus is responsible for nitrogen release control Average amount of nitrogen in humus is 5%. Soil with 1% organic matter has about one 1000 lbs of nitrogen per acre. Only about 2% of that amount is released annually for crop use. PHOSPHORUS Phosphorus is NOT like nitrogen and does not travel through soil easily. It moves with soil particles so is lost through plant use or erosion. Very little phosphorus moves through the soil Phosphorus is most important to new seeds and plants Most effective in high amounts near root area Soil pH greatly effects phosphorus-too high or too low pH converts phos to unusable compounds. Sources for phos-Diammonium phosphate and triple superphosphate, animal manures, sludges, plant residues, ground rock phosphate and apatite Potassium Second only to nitrogen in amount used by plants Relatively immobile in soil. Moves in sandy soils Most common sign of deficiency is scorching or browning on leafs. Highest nutrient found in soil Low amounts available to plants Bound in clay soil particles Comes from mined waters. Largest deposit is in Saskatchewan, Canada. Secondary Nutrients The difference between secondary and primary nutrients is simply that the plant uses them in smaller amounts. Still essential to plant growth and development. There are three secondary nutrients: Sulfur, Calcium and Magnesium. Sulfur Becomes available after decomposition of organic matter and plant residues. The available form is SO4—Sulfate and behaves in soil much like nitrate Sulfur Continue Water logged soils may make sulfur unavailable Can be supplied by rainwater Is a fertilizer impurity Adding gypsum will add sulfur Is an ingredient of many proteins, enzymes and amino acids of the plant Interesting fact-helps give mustard, onion and garlic it’s flavor Calcium Supplied to plants by soil minerals, organic materials, fertilizers and liming materials. Because of cation exchange-soil is very attracted to calcium. Calcium Continued Essential for plant cell-wall structure, element transport and retention and strength in the plant. Exist in a balance with Magnesium and Potassiumtwo much of any one of them results in harmful insufficiencies of the other two. Magnesium Supplied to plants through soil minerals, organic material, fertilizers and limestone. Strong positive cation exchange and acts like Calcium and Potassium Is essential for photosynthesis Activates enzymes for plant growth Very mobile-goes where it is needd Micronutrients 7 0f the 16 essential plant nutrients that are required in small amounts. They are: Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mo) and Chlorine (Cl). Will limit plant growth under the following conditions: Highly leached acid sandy soil Muck Soils Soils high in pH or lime content Soils that have been heavily cropped and heavily fertilized with macronutrients Iron Part of many organic compounds Essential for chlorophyll-gives plants their green color Highly reactive with Manganese Copper Essential for growth and activates many enzymes Lack of will effect proteins in plant Too much copper causes shortages in Iron Manganese Basically absorbed by plants Activates enzymes Zinc Essential for plant growth Molybdenum Required in minute amounts Aids in Nitrate fixation and reduction Boron-regulates metabolism Nutrient Availability and Plant Uptake Available nutrients are located near the surface of soil particles. Roots come in contact with nutrients and take them up into the plant. Soil may and does contain large amounts of nutrients but only a small percentage is available for the plant to take up. Some nutrients will simply stay in the soil until converted to usable forms Some amount of nutrient is lost through erosion, leaching or volatilization Nutrient Unavailability Insoluble chemical compounds-phosphorus and micronutrients included in many of these (does not dissolve in water) Unweathered or undecomposed soil minerals or rock fragments-most nutrients included Organic matter or plant residues-the main ones are nitrogen and sulfur Trapped by soil particles-potassium and some ammonium Soil pH greatly influences nutrient availability. Too high or too low can make nutrients unavailable by converting them to insoluble chemical compounds Soil pH Soils contain both acids and bases and the amounts are expressed as pH Scale ranges from 0 to 14 Soils below 7 contain acid and are acidic or sour Soils above 7 are base and are alkaline or sweet Soils that are 7 are neither acidic or alkaline These differences effects how nutrients are taken up by the plant. Causes of Acid Soil Removal of calcium, magnesium and potassium from a soil profile will allow soil acids to move in. Conversion of ammonium fertilizers to nitrates Adjusting Soil pH Soil can be adjusted-AFTER soil test Lime is used to adjust pH upward-neutralizer Sulfur lowers pH 2 lbs/1000ft2 for each .1 unit of pH Iron and Aluminum can also lower pH Lime Sources Most common is agricultural Limestone Contains calcium and magnesium-positive cations Functions of Lime Sweetens the soil Improves the availability of plant nutrients Increase the effectiveness of applied nitrogen, phosphorus and potassium. Increase the activity of microorganisms, including those responsible for nitrogen fixation in legumes and the decomposition or organic matter. Improves plant growth and crop yields. Beans 6.0-7.5 Lettuce 6.0-7.0 Blueberry 4.0-6.0 Onion 6.0-7.0 Cabbage 6.0-7.5 Potato 4.5-6.0 Cantaloupe 6.5-7.5 Rhubarb 5.5-7.0 Carrot 5.5-7.0 Strawberry 5.0-7.5 Grape 6.0-7.0 Tomato 5.5-7. Azalea 4.5-6.0 Junipers 5.0-6..5 Carnation 6.0-7.5 Petunias 6.0-7.5 Chrysanthemum 6.0-7.0 Pansies 5.5-7.0 Daffodil 6.0-6.5 Roses - Hybrid Tea 5.5-7.0 Geraniums 6.0-8.0 Roses - Climbing 6.0-7.0 Hydrangea - blue 4.0-5.0 Spruce 4.5-5.5 Hydrangea - pink 6.0-7.0 Rhododendron 4.5-6.0 Soil Sampling Before attempting to adjust pH or add fertilizers, soil samples must be taken. Sample must be representative of the soil that is to be treated. Take cores from several areas throughout total field, lawn or garden Soil probes, shovel, bucket Mix all the core samples together well Take one sample from composite to test Foliar Symptoms Foliar systems-abnormalities in leaves, stems or petals that show nutrient deficiencies, insect issues, disease, drought and pesticide damage. Tissue Testing-Rapid and Dry Rapid Tissue Testing Green tissue is used Chemicals are used Quick but not always accurate Dry Tissue Testing Dried leaves or plants Whole is ground up and sample taken Reliable and repeatable Not recommended for fertilizer needs Fertilizer Placement Proper placement of fertilizer is very important to the effectiveness of the nutrients. Characteristics of the soil, kind of crop and the nature of the fertilizer have to be taken into consideration. Provide adequate quantities of plant nutrients with the root zone. Irregular distribution can lower fertilizer efficiency Early stimulation of the seedling is usually advantageous. Placement in root zone is good. The rate and distance of fertilizer movement depends upon the character of the soil. Nutrient elements may move upward during dry periods and may be carried downward by rain or irrigation water. Soil-supplied nutrients when in dry soils are of little or no benefit to the plant. Excessive amounts of fertilizer can be injurious. Crops vary in tolerance to soluble salts. Important to place phosphorus near roots as it travels slowly and is most effective at roots Fertilizer needs to be watered in to reduce risk of salt injury Foliar Fertilization Feeding plant through leaves and stems Supplemental feeding Not effective Used for rapid intake of a particular nutrient to correct a deficiency problem Animal Manure Plant nutrient content is generally low but contains most of the essential nutrients Even in small amounts manure can supply enough of especially micronutrients to fill in the gaps. Nutrient amount is variable and dependent on many factors: age and kind of animal, feed consumed, amount and kind of litter/bedding used and handling methods.