Nutrient Cycling

1. Nutrient Cycling Mike Hubbs USDA-NRCS National Nutrient Management Specialist Washington DC NRCS Conservation Bootcamp

2. Nutrient Cycling N P C K NRCS Conservation Bootcamp

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4. Essential Plant Nutrients A plant nutrient is considered essential if: 1) a deficiency of the element makes it impossible for the plant to complete its life cycle (plant will die) 2) the deficiency cannot be corrected by substituting another element 3) the element is needed by a wide variety of species from many different plant families NRCS Conservation Bootcamp

5. Essential Plant Nutrients • Green plants need 16 essential nutrients • Plants get C, H, and O from air & water • The remaining 13 elements come from soil • N, P, K, Ca, Mg, S, B, Cl, Cu, Fe, Mn, Mo, and Zn NRCS Conservation Bootcamp

6. Essential Plant Nutrients C. HOPKIN’SCaFe, Mighty fine CuZine, Motley Manager, Burley Clerk NRCS Conservation Bootcamp

7. Essential Elements • Primary – N, P, & K • Secondary – Ca, Mg, & S • Minor – Zn, B, Mo, Cu, Fe, Mn, & Cl NRCS Conservation Bootcamp

8. Primary Nutrients Form Taken Major Concentration Elementup by plantsSource in plants Nitrogen (N) NO3-, NH4+ Org. matter, 1 – 6% atmosphere Phosphorus (P) H2PO4-, HPO42- Minerals, 0.05 – 1.0% org. matter Potassium (K) K+ Soil minerals 0.3 – 6.0% NRCS Conservation Bootcamp

9. Carbon 1) Function in plants a) Carbon is part of the structural component of plant as well as the seed component. b) CO2 is assimilated in the plant leaf via photosynthesis c) Carbohydrates are end products of photosynthesis and are used for energy and respiration. NRCS Conservation Bootcamp

10. Carbon (cont.) • Content in soil, plants, and air a) Carbon is approximately 58% of SOM b) Carbon is approximately 40% of plant dry weight c) CO2 is approximately 370 ppm (0.03 %) in the atmosphere NRCS Conservation Bootcamp

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12. Soil Carbon Cycle ATMOSPHERE CO2 O2 Photosynthesis O2 CO2 Decomposition and exudation Root respiration Microbial respiration Plant uptake Soil organic matter including humus & microbial biomass O2 CO2 Rapid release SOIL Slow mineralization Modified from Rowell (1994) NRCS Conservation Bootcamp

13. Nitrogen 1) Function in plants a) N is a major constituent of protein b) N in chlorophyll, nucleic acids, enzymes, and many other cellular compounds c) N is mobile within the plant and when a deficiency occurs in lower leaves NRCS Conservation Bootcamp

14. Nitrogen (cont’d) 2) Content of N in crops, atmospheric emissions and depositions of N, & available amounts in soils a) soil often contains 2,000-6,000 lb N/ac in the plow layer (acre furrow slice) b) 4.5-13.5 lb N/ac per yr is deposited by precipitation NRCS Conservation Bootcamp

15. Nitrogen (cont’d) 3) Chemical form of N in soils a) Approximately 95% N – organic form b) NH4+ and NO3- is mineralized and is available d) NO3- can be denitrified to N2 and N2O gases e) atmospheric N2 can be fixed into nodules by legumes NRCS Conservation Bootcamp

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17. The Nitrogen Cycle Atmospheric N2 Volatilization loss of NH3 Removed from soil/plant system by harvesting Industrial fixation Symbiotic fixation (legumes) Surface application of urea, manure, or biosolids Nitrogen fertilizer Deposition of NO3- by precipitation Gaseous loss of N2,N2O Manure, biosolids Crop residue Soil organic matter (Organic N) Plant uptake 1.Ammonification 4. Denitrification 3. Immobilization Ammonium N (NH4+) 2. Nitrification Nitrate N (NO3-) Removed from soil/plant system by leaching NRCS Conservation Bootcamp

18. Phosphorus and Potassium Mike Gangwer USDA-NRCS Michigan Nutrient Management Specialist East Lansing, MI NRCS Conservation Bootcamp

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20. Phosphorus 1)Function in plants a) P is a major constituent of the nucleus of plants, b) P is also found in compounds ADP and ATP that store and transfer energy within the plant, c) P is involved in nearly all metabolic processes NRCS Conservation Bootcamp

21. Phosphorus (cont’d) • Content of P in crops and available amounts in soils a) soils generally contain 50-1,500 ppm (100-3,000 lb/ac) b) soluble forms of fertilizer P are quickly converted to less available forms when added to soils. c) concentration of P in soil solution is usually <0.01 to 1 mg/L (ppm) [0.1-0.3 ppm for agronomic crops] d) most crops contain 0.1-0.5% P (1,000 to 5,000 ppm Dry Weight) NRCS Conservation Bootcamp

22. Phosphorus (cont’d) • Chemical forms of P in soils a) H2PO4- > HPO42- pH below 7.2 b) HPO42- > H2PO4- pH above 7.2 (calcareous soils) These are the forms of P absorbed by plants NRCS Conservation Bootcamp

23. Phosphorus (cont’d) • Chemical forms of P in soils c) weathering causes secondary P fixation of Ca, Fe, and Al phosphates d) alkaline soils, Ca phosphates form e) acidic soils, Fe and Al phosphates form f) soil Fe and Al oxides, and some clays fix soluble P These forms of P are unavailable for plant absorption NRCS Conservation Bootcamp

24. Soil P and Nutrient P2O5 Relationships ● ppm P x 2 = lb P/acre (or pp2m) 2,000,000 lb/afs (afs = acre furrow slice) ● lb P x 2.3 = lb P2O5 ● for nutrient additions from fertilizers & organic residuals (example: manure), use lb of P2O5 ● for P removal by plants, use lb of P2O5 ● for soil test P (STP) levels, use “lb P” or “ppm P” NRCS Conservation Bootcamp

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27. Municipal & Industrial By-Products Agricultural Residuals Erosion, Runoff Sediment & Soluble P Plant Residues Fertilizer Plant Uptake Sorbed P Clays Al, Fe Oxides Sorption Soil Solution P HPO42- & H2PO4- Desorption Dissolution Immobilization Secondary P Minerals Ca, Fe, Al phosphates Precipitation Mineralization Organic P Soil Biomass (living) Soil Organic Matter Soluble Organic P Dissolution Leaching Primary P Minerals Apatites NRCS Conservation Bootcamp (Redrawn from Pierzynski et al., 1994)

28. Potassium NRCS Conservation Bootcamp

29. Potassium (cont’d) 1) Function in plants a)unlike N and P, K+ does not become part of organic compounds in plants b) K+ is involved in water uptake from soil, water retention in plant tissue, and transport of water within the plant c) K+ balances the negative charges of organic and inorganic anions d) K+ helps maintain turgor, or cell pressure NRCS Conservation Bootcamp

30. Potassium (cont’d) 2) Content of K+ in crops and available amounts in soils a) soils generally contain over 20,000 ppm (40,000 lb/ac) of K+ b) nonexchangeable K+ within clay mineral layers is fixed c) exchangeable K+ on clay mineral surfaces and K+ dissolved in the soil solution (usually 1-10 ppm) are available for plant absorption NRCS Conservation Bootcamp

31. Potassium (cont’d) 3) Chemical forms of K in soils a) as soils weather, K minerals release K+ ions for adsorption onto cation exchange sites (CEC) b) occurs in soil solution as K+ ions and are available to plants for absorption c) quantities in soils will vary greatly d) excess exchangeable K+ levels can induce a Mg2+ deficiency in plants (dairy feed ration) NRCS Conservation Bootcamp

32. Soil P and Nutrient K2O Relationships ● ppm K x 2 = lb K/acre (or pp2m) 2,000,000 lb/afs (afs = acre furrow slice) ● lb K x 1.2 = lb K2O ● for nutrient additions from fertilizers & organic residuals (example: manure), use lb of K2O ● for K removal by plants, use lb of K2O ● for soil test K (STK) levels, use “lb K” or “ppm K” NRCS Conservation Bootcamp

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34. Component Input to soil Loss from soil The Potassium Cycle Animal manures and biosolids Crop harvest Plant residues Mineral fertilizers Runoff and erosion Exchangeable potassium Plant uptake Soil solution potassium (K+) Fixed potassium Mineral potassium Leaching NRCS Conservation Bootcamp Potash & Phosphate Institute

35. Summary • Know the importance of nutrient cycling through the farm system. • Know the chemical forms of CNPK in terms of organic and inorganic specie. • Know that for developing a nutrient management plan as part of a Conservation Plan, the planner will use the criteriain state eFOTG 590 Standard Nutrient Management. NRCS Conservation Bootcamp

36. Thank you NRCS Conservation Bootcamp