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Phosphorus and Phosphorus Management

This outline covers the importance of phosphorus in crop growth, soil reactions, water quality, and nutrient management to address environmental concerns. Explore key topics such as phosphorus cycle, forms, sources, and sustainable management practices.

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Phosphorus and Phosphorus Management

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  1. Phosphorus and Phosphorus Management

  2. Outline • Introduction • P Sources • P Transport • Environmental Concerns • P Management • Summary

  3. Introduction P-Crop Need P Forms P Cycle Reactions in Soil (fate of P) P Buffer Capacity Outline • P Sources • P Transport • Environmental Concerns • P Management • Summary

  4. Plants need P for growth ATP DNA RNA P deficiency: stunted and spindly purplish foliage (older leaves) IntroductionP-Crop Need

  5. IntroductionP-Crop Need Goal of soil testing = determine crop need - Examples of agronomic soil P tests: Bray P1, Mehlich III, Olsen

  6. IntroductionP-Crop Need

  7. Inorganic P Fertilizers, soluble P PO43-, HPO42-, H2PO4- Immediately available Organic P Manure, plant/leaf residues Inositol phosphates, nucleic acids, phospholipids Slowly available (needs to be mineralized to inorganic form) IntroductionP Forms AS RELATED TO CROPS, SOILS, AND FERTILIZERS

  8. Soil Test P estimates plant available P usually Bray P1 (in WI) expressed in ppm P (elemental P, not P2O5) Phosphate = P2O5 (oxide) fertilizer recommendations and product analysis given in oxide form conversion factors: 1 lb P = 2.29 lb P2O5 1 lb P2O5 = 0.44 lb P IntroductionP Forms AS RELATED TO CROPS, SOILS, AND FERTILIZERS

  9. IntroductionP Forms AS RELATED TO WATER QUALITY • Particulate P (PP) • definition: P bound to eroded sediment or organic matter • also called sediment-P • Soluble P (SP) • definition: P dissolved in runoff (working definition: P that passes through a 0.45 micron filter) • also called dissolved P (DP), dissolved reactive P (DRP), and ortho-P • Total P (TP) • definition: total amount of P, both PP and SP, in soil or runoff

  10. IntroductionP Forms AS RELATED TO WATER QUALITY • P Concentration • definition: amount of P per volume • expressed as: mg P/L or ppm • P Load • definition: total amount of P delivered • expressed as: mg P/ha (lb P/acre)

  11. IntroductionP Cycle

  12. IntroductionP Reactions in Soil • Mineralization and Immobilization (organic P) Immobilization microbes Fe3+, Al3+, Ca2+ Organic P forms H2PO4- Fe, Al, Ca phosphates microbes insoluble fixed P soluble phosphate Mineralization

  13. IntroductionP Reactions in Soil • Adsorption and Desorption • Clays, Fe and Al oxides, organic matter • Precipitation/Dissolution • Acid soils – Fe, Al, Mn compounds dominate • Alkaline soils – Ca compounds dominate What happens when fertilizer or manure P is added to soil? P is quickly and strongly bound to soil particles. (inorganic P)

  14. IntroductionBuffer Capacity • P buffer capacity (indication of the rate of change of STP with additions or removals) Ave 18 lbs P2O5/acre to change STP by 1ppm (Leikam, 1992) • Time is needed to raise OR lower STP

  15. Outline • Introduction • P Sources • Soil • Plants • Fertilizers • Manures • Livestock Feed • Municipal Waste • P Transport • Environmental Concerns • P Management • Summary

  16. P SourcesSoil P occurs naturally in soil (but usually in very low concentrations)

  17. P SourcesPlants • Vegetation can contribute P to runoff • plants release P when tissue is ruptured due to freezing, thawing, and drying

  18. P SourcesFertilizers • Added to soil to increase fertility for crop production • Common examples: N-P2O4-K2O • Monoammonium phosphate: NH4H2PO4 11-48-0 • Diammonium phosphate: (NH4)2HPO4 18-46-0 • Triple superphosphate: Ca(H2PO4)2 0-46-0 • Easily soluble to runoff water (if rain comes shortly after application)

  19. P SourcesManure • Manure contains nutrients for plant growth, including P • Manure applications improve physical properties of soil • Manure applications can lead to buildup of soil P

  20. P SourcesManure Note: Manure supplies approximately equal amounts of N and P.

  21. P SourcesLivestock Feed • Farm animals need adequate protein, energy, and nutrition • Dietary rations often contain excess nutrients, particularly P

  22. P SourcesIndustrial and Municipal Waste • Water discharged from wastewater treatment facilities • Storm water runoff • Biosolids www.milorganite.com

  23. Outline • Introduction • P Sources • P Transport • Runoff and Erosion • P Leaching • Environmental Concerns • P Management • Summary

  24. Runoff =movement of water across the land’s surface Erosion =movement of soil particles by water P TransportRunoff and Erosion Runoff and erosion are SURFACE WATER quality problems.

  25. P TransportLeaching • Leaching =infiltration of water through soil to groundwater (low on most Wisconsin soils) P leaching is a GROUNDWATER quality problem

  26. P TransportLeaching Nutrient and Pest Management Program

  27. Outline • Introduction • P Sources • P Transport • Environmental Concerns • Eutrophication • Soil Test P • Point/NonPoint Pollution • Urban/Agricultural • P Management • Summary

  28. Environmental ConcernsEutrophication • Too little P = land degradation • Too much P = eutrophication What happens when a stream or lake receives more P than it is used to receiving?

  29. Environmental ConcernsEutrophication P moves from soil to stream P stimulates algae growth Too much algae blocks sun, uses oxygen Fish can die, stream health declines = Odor, limits recreational uses, lowers drinking water quality

  30. Environmental ConcernsSoil Test P Accumulation of P as a result of inputs exceeding removals

  31. Environmental ConcernsSoil Test P As soil test P increases, the amount of P dissolved in runoff also increases. Natural runoff from April through July on corn plots at Arlington.

  32. Environmental ConcernsSoil Test P N-based nutrient management strategy lbs/acre N needs met, but as a result, twice as much P as needed was applied. 160 320 120 60 45

  33. Environmental ConcernsSoil Test P P-based nutrient management strategy lbs/acre P needs met, but will need supplemental N AND more acres to apply manure. 160 160 80 60 45

  34. Environmental ConcernsPoint/Nonpoint Pollution • Point source pollution: Identifiable pollution discharge sources. • Nonpoint source pollution: Diffuse, hard-to-identify pollution sources transported by runoff and erosion from a widespread land area.

  35. Environmental ConcernsUrban/Agricultural • Urban sources of P: • lawns: leaves, soil, fertilizer, animal droppings, plants • wastewater • biosolids • Agricultural sources of P: • manure • fertilizer • crop tissue • soil

  36. Outline • Introduction • P Sources • P Transport • Environmental Concerns • P Management • Approaches to Improve P Balance • Management to Reduce P Losses • Summary

  37. P Management - Improve P Balance NPM Program

  38. P Management - Improve P Balance Follow Soil Test Recommendations • At optimum STP, recommended nutrients = anticipated crop removal • Soil test every 3-4 years

  39. P Management - Improve P Balance Credit Nutrient Sources • Credit manure P BEFORE determining supplemental fertilizer application rates • Manure can supply crop nutrients as effectively as commercial fertilizers • Need nutrient content and application rate Lab analysis or book value Calibrate!

  40. P Management - Improve P Balance Use Starter Judiciously • Recommendation: for corn band apply starter fertilizer if needed (10 lb N, 20 lb P2O5, 20 lb K2O) • On soils in the excessively high range for P, avoid starter applications in excess of 10-20-20

  41. P Management - Improve P Balance

  42. P Management - Improve P Balance Manage Dietary P Goal: avoid overfeeding P FOLLOW DIETARY P GUIDELINES • Dairy • know P content of dietary supplements • NRC recommends between 0.32 and 0.38%P, depending on milk production • Swine/Poultry • improve efficiency • consider feeding HAP corn • consider adding phytase enzyme to feed

  43. P Management - Improve P Balance Manage Dietary P Phosphorus level in the manure is directly related to the level of P intake. % P in diet Source: Powell et al, 2001

  44. P Management - Improve P Balance Manage Dietary P Dairy manure applied at 25 ton/a Source: Ebeling et al, 2002

  45. P Management - Improve P Balance Manage Dietary P One year after manure application, the cumulative runoff dissolved P losses were significantly higher from the plots with high P diet manure compared to the low P diet manure and control. Source: Ebeling et al, 2002

  46. P Management - Improve P Balance Increase land base • Ensure all cropland receives manure sometime during the rotation • Apply manure to rented land • Obtain manure application rights from neighboring grain farmers

  47. Source Transport P LOSS P Management - Reduce P Loss In order for P to reach surface water: need both a SOURCE of P and MOVEMENT of P

  48. P Management - Reduce P Loss Identify low risk sites • Source and transport – site specific: • P Index: http://wpindex.soils.wisc.edu • SNAP-Plus: www.snapplus.net

  49. P Management - Reduce P Loss Identify low risk sites Total Risk Index (PI) = [Soluble P + Particulate P + Acute P] * total P delivery ratio Needed for PI calculations: -management, cropping rotations, tillage, fertilizer and manure applications, soil test P, slope, distance to surface water, etc.

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