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Nutrient Management: Phosphorus, Potassium, Heavy Metals

Learn about the cycles, management strategies, environmental concerns, and practical applications of phosphorus, potassium, and heavy metals in agriculture. Understand crop removal rates, nutrient testing, and best practices for sustainable farming.

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Nutrient Management: Phosphorus, Potassium, Heavy Metals

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  1. Nutrient Management Section 5.5 – Phosphorus, Potassium and Heavy Metals Adapted CNMP Core Curriculum Presented by: Roberto Maisonnave, Ag Engineer & M. Sc. International Environmental Consultant robermaison@hotmail.com www.ambientagro.com

  2. Objectives • Understand the P cycle • Learn effects of P in the environment • P management exercise • Understand K+ cycle and management • Review main Heavy Metals related issues

  3. Crop Residue The Phosphorus Cycle Crop Harvest Fertilizer P Manure P Solution P Stable Labile Labile Stable Organic P Inorganic P Leaching From: Livestock and Poultry Environmental Stewardship 34-3

  4. Critical Maintenance Level Limit Nutrient Rate Buildup Drawdown Soil Test Level Soil Phosphorus • Maintaining the soil solution concentration for plant uptake is important. • Nutrient strategy Range Range Maintenance Range

  5. Soil Test Phosphorus • Agronomic soil tests are used to determine plant available P. • The tests are a prediction of the amount of desorbed labile (readily available) P into soil solution from the soil mineral surface, over the growing season.

  6. Environmental Concerns • Phosphorus is adsorbed to soil particles and moves with soil • Pathways that transport soil to surface water are the primary pathways for P movement to surface water

  7. Pathways for P Loss from Soils

  8. Phosphorus in Water • Often limiting nutrient in fresh water systems • Addition stimulates algal growth • Too much P = less dissolved O2 • Excessive P = EUTROPHICATION

  9. Managing Agricultural P • Minimize P sources • Diet manipulation • Manure technologies - No reduction in P, but may increase options for hauling greater distances or marketing • Fertilizer Management • Conservation Practices • No direct application of P to water

  10. Dietary Manipulation Manure Treatment Less Available P in Manure Agronomic Application Rates Erosion Control Buffer Strips Improved Water Quality

  11. CNMP Development • Create a Farm P Balance • Current soil tests • Current manure tests • Determine crop P needs • Use manure and wastewater volumes and manure test to determine P2O5 to be applied • Use risk assessment tools to determine the lowest risk application areas

  12. P Based Application Rate • Soil Test Phosphorus (STP) • Application based upon soil test analysis, and crop P needs, based on university recommendations • Fertility strategy • Buildup low P soils • Maintenance • Drawdown

  13. Kansas P Field Category & Application Rates

  14. Kansas Manure Application Rates Oklahoma Manure Application Rates

  15. Phosphorus & Potassium Crop Removal

  16. Phosphorus Removal • Corn removes 9 kg P2O5 / ton grain • 9 ton/ac Corn: 81 kg P2O5 / ha • This corn crop would remove approximately 62 kg of P2O5per hectare

  17. Example NE 25

  18. Example NE25

  19. POTASSIUM

  20. Potassium • Potassium Cycle • Ruminant considerations • Dairy herds, primarily lactating cows • Potassium management

  21. The Potassium Cycle

  22. Potassium characteristics • Soils can have > 20.000 kg Total K+ / ha • Almost all fixed in clay bridges and unavailable for plant uptake • Exchangeable K+ is bound to soil particle surfaces, and is desorbed into soil solution at 1-10 ppm • Not easily leached in soils, but can be leached

  23. Excess K+ Concerns • Grass Tetany • High levels of K+and N in the plant can cause reduced amounts of plant magnesium (Mg) • This can cause a Mg deficiency in grazing animals, and cause a condition called grass tetany or hypocalcaemia • Avoid over-application of K+to pastures • Environmental Concerns • Generally, excess K+ in surface water has not been a concern • Agronomic considerations • Soil Test • Provide adequate K for crop production

  24. N-P-K Summary • Understand the source and transport characteristics of the landscape and the particular behavior of elements • Develop a crop budget using nutrient strategies and risk assessment tools • Evaluate performance using good records • Check (often) laws, permit requirements, and regulations governing nutrient management

  25. HEAVY METALS

  26. Who are they? Are they important? • Ag+, As • Cd2+, Co2+, Cr, Cu2+ • Fe, Hg2+, Ni2+, Pb2+, V, Zn2+ • Some have no biological function • Others are essential for life but toxic at high concentration levels

  27. HEAVY METALS CONCERNS • Started on Bronze Age: melting of Cu & Sn • Drinking water pollution • Products for direct human consumption • Vegetables & Fruits • Grains • Fish: Minamata Bay case, Hg bioaccumulation • Hg water: 2 ppb, Hg fish: 20.000 ppb • Respiratory disease

  28. Corn* Crop Removal Source: Kansas State University, Corn Production Handbook * 10 ton / ha yield

  29. Swine Manure HM Source: AmbientAgro Swine Effluent Database Anaerobic Lagoon Effluent

  30. Swine Manure HM in Northeast China Source: Zhang et. al; 2012. Journal of Environmental Research and Public Health

  31. Take home message • Heavy metals are present at your farm • Nutrition science must help reducing concentrations in feed additives • Be aware of their risk especially in relation to direct human consumption crops • Soil thresholds: may be wise to follow Bio solids annual loading rates (EPA)

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