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Plant Nutrition

Plant Nutrition. INTRO TO SOILS CH 12. Plant Nutrition. Many soil factors affect plant growth Difficult/expensive to improve However . . . Supply of soil nutrients can be controlled. Plant Nutrition Essential Elements. Nitrogen Promotes rapid growth and dark green color

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Plant Nutrition

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  1. Plant Nutrition INTRO TO SOILS CH 12

  2. Plant Nutrition Many soil factors affect plant growth Difficult/expensive to improve However . . . Supply of soil nutrients can be controlled . . .

  3. Plant NutritionEssential Elements Nitrogen • Promotes rapid growth and dark green color • Needed for chlorophyll production • Key component in protein • Plant water efficiency

  4. Plant NutritionEssential Elements However, too much Nitrogen . . . • Produces soft, weak, easily injured growth (lodging) • Prone to disease/insect injury • May slow maturity and ripening • Delays hardening-off • May impair flavor in some vegetables • Nitrates may accumulate

  5. Plant NutritionEssential Elements Nitrogen is most important for crops grown for their vegetation, such as leafy vegetables, hay or turfgrass

  6. Nitrogen Cycle • Nitrogen moves around . . . • Atmosphere is ~ 78% N2 • Unfortunately, N2 (gas) is an unusable form for plants However . . .

  7. Nitrogen Cycle Bacteria can use this form; they may . . . • Use it to form protein for their own bodies, or . . . • Supply it to host plants • Eventually, both microbes and host plants do die; • This allows other microbes to . . .

  8. Nitrogen Cycle Mineralize the protein to ammonium ions (NH4+) • NH4+may be . . . • taken up by plants • converted by bacteria (Nitrification) to NO3- • lost to the atmosphere (Volatilization) as NH3 • See reaction p. 198 (NH4+ with Hydroxyl ions)

  9. Nitrogen Cycle • Study the Nitrogen Cycle (simplified) on p. 199 and Nitrogen Cycle handout • Additionally, lightning and fertilizerfactoriesfixN

  10. Nitrogen Cycle Non-biological losses of nitrogen include: • Leaching of NO3- • Ammonia Volatilization* *may occur in dry, alkaline, or recently limed soil

  11. Nitrogen Cycle Losses through production: • Crop harvest • Erosion • Irrigation • Liming

  12. Nitrogen Cycle Additions for production • Manuring • Growing legumes • Fertilizing

  13. Forms of Nitrogen in Soil 97-99% of soil nitrogen resides in organic matter • only a small percentage is mineralized to useable forms • average of 90 lbs/acre/yr . . . far short of typical crop needs • e.g. 150-bushel/acre corn crop contains ~ 190 lbs of nitrogen • See fig. 12-6, p. 201 Know this chart!

  14. Nitrogen Deficiency Symptoms: • Slow growth and stunting • Lack dark green color • Exhibit chlorosis • Lower leaves first affected • Grasses begin yellowing at blade tips • Extreme cases dry up – called “firing”

  15. Phosphorus “Partners” with Nitrogen • Part of genetic material • ATP stores and transfers energy • Spurs early and rapid root growth • Helps plants use water more efficiently resist cold and disease and improve quality of grains and fruits • Improves efficiency of Nitrogen uptake

  16. Phosphorus “Balances” Nitrogen • Hastens maturity • Aids blooming and fruiting • Important in crops flowers, fruits, seeds • Promotes early and rapid root growth • Major element in starter fertilizers

  17. Forms of Phosphorus in Soil • Provided by weathering of mineral . . . Apatite (calcium phosphate) • Anions are: H2PO4- HPO4-2 (referred to as phosphate ions)

  18. Forms of Phosphorus in Soil • Much phosphorus is unavailable to plants • “fixed” in insoluble forms • Iron phosphates in strongly acid soils • Aluminum phosphates in moderately acid soils • Calcium phosphates in alkaline soils Maximum availability between 6.0 to 7.0

  19. Phosphorus Deficiencies/Excesses • P-deficient plants often have a purple tint • Older, lower leaves affected first • May exhibit darker than normal green color • Delayed maturity and poor root systems • Excess P ties up nutrients such as iron (Fe)

  20. Potassium • a.k.a. – Potash • Elemental symbol “K” • Plants consume more K than any other nutrient except N • Cell walls and stems strength • Regulates stomates • Fruit development and ripening • Root and tuber crops • Potassium promotes tougher growth

  21. Potassium Improves: • Stem strength; less prone to lodging • Fight disease • Increase winter hardiness • Influences transpiration rate; conserves water supplies • Caution: excess/luxury consumption may inhibit uptake of calcium or magnesium

  22. Potassium in the Soil • Weathering releases Potassium ions (K+) • Stored on CEC and fixation in clays (fig. 12-11, p. 206) • Moves in soil: more than P, less than N • Most plant uptake occurs by diffusion

  23. Potassium Deficiencies • Less of a problem than other primary nutrients; some occurrence in sandy, leached soils • Excess N can inhibit uptake of K • Dry, cold, poorly aerated soil inhibits uptake; neutral pH is desirable for uptake • Deficiencies are seen as “marginal scorch” on edges of lower, older leaves

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