Phosphorus and Phosphorus Management

Outline − Introduction − P Sources − P Transport − Environmental Concerns − P Management − Summary

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

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

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

Introduction P-Crop Need Soil test P, ppm CropOptimum No response Alfalfa18-25>35 Corn15-20>30 Soybean10-15>20 Medium and fine-textured soils, Bray P-1 test.

Introduction P Forms − Inorganic P − Fertilizers, soluble P − PO 4 3-, HPO 4 2-, H 2 PO 4 - − Immediately available − Organic P − Manure, plant/leaf residues − Inositol phosphates, nucleic acids, phospholipids − Slowly available (needs to be mineralized to inorganic form) AS RELATED TO CROPS, SOILS, AND FERTILIZERS

Introduction P Forms − Soil Test P − estimates plant available P − usually Bray P1 (in WI) − expressed in ppm P (elemental P, not P 2 O 5 ) − Phosphate = P 2 O 5 (oxide) − fertilizer recommendations and product analysis given in oxide form − conversion factors: 1 lb P = 2.29 lb P 2 O 5 1 lb P 2 O 5 = 0.44 lb P AS RELATED TO CROPS, SOILS, AND FERTILIZERS

Introduction P Forms − 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 AS RELATED TO WATER QUALITY

Introduction P Forms − 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) AS RELATED TO WATER QUALITY

Introduction P Cycle

Introduction P Reactions in Soil − Mineralization and Immobilization (organic P) Organic P formsH 2 PO 4 - Fe, Al, Ca phosphates Fe 3+, Al 3+, Ca 2+ soluble phosphate microbes insoluble fixed P Immobilization Mineralization

Introduction P 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 (inorganic P) What happens when fertilizer or manure P is added to soil? P is quickly and strongly bound to soil particles.

Introduction Buffer Capacity − P buffer capacity (indication of the rate of change of STP with additions or removals) Ave 18 lbs P 2 O 5 /acre to change STP by 1ppm (Leikam, 1992) − Time is needed to raise OR lower STP

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

P Sources Soil P occurs naturally in soil (but usually in very low concentrations) Form Concentration (ppm) Total Soil Test P (agronomic) Soil Solution

P Sources Plants − Vegetation can contribute P to runoff − plants release P when tissue is ruptured due to freezing, thawing, and drying

P Sources Fertilizers − Added to soil to increase fertility for crop production − Common examples: N-P 2 O 4 -K 2 O − Monoammonium phosphate: NH 4 H 2 PO − Diammonium phosphate: (NH 4 ) 2 HPO − Triple superphosphate: Ca(H 2 PO 4 ) − Easily soluble to runoff water (if rain comes shortly after application) (if rain comes shortly after application)

P Sources Manure − Manure contains nutrients for plant growth, including P − Manure applications improve physical properties of soil − Manure applications can lead to buildup of soil P

P Sources Manure Livestock --Nitrogen (N)-- PhosphatePotash Surface Incorpor- ated (P 2 O 5 ) (K 2 O) ---Solid lbs/ton--- Dairy3437 Beef3559 Swine7967 Chicken Note: Manure supplies approximately equal amounts of N and P.

P Sources Livestock Feed − Farm animals need adequate protein, energy, and nutrition − Dietary rations often contain excess nutrients, particularly P

P Sources Industrial and Municipal Waste − Water discharged from wastewater treatment facilities − Storm water runoff − Biosolids

Outline − Introduction − P Sources − P Transport − Runoff and Erosion − Environmental Concerns − P Management − Summary − P Leaching

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

P Transport Leaching − Leaching =infiltration of water through soil to groundwater =infiltration of water through soil to groundwater (low on most Wisconsin soils) P leaching is a GROUNDWATER quality problem

P Transport Leaching Nutrient and Pest Management Program

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

Environmental Concerns Eutrophication What happens when a stream or lake receives more P than it is used to receiving? − Too little P = land degradation − Too much P = eutrophication

Environmental Concerns Eutrophication 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

Environmental Concerns Soil Test P Accumulation of P as a result of inputs exceeding removals

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

Environmental Concerns Soil Test P N-based nutrient management strategy lbs/acre N needs met, but as a result, twice as much P as needed was applied.

Environmental Concerns Soil Test P P-based nutrient management strategy P needs met, but will need supplemental N AND more acres to apply manure. lbs/acre

Environmental Concerns Point/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.

Environmental Concerns Urban/Agricultural − Urban sources of P: − lawns: leaves, soil, fertilizer, animal droppings, plants − wastewater − biosolids − Agricultural sources of P: − manure − fertilizer − crop tissue − soil

Outline − Introduction − P Sources − P Transport − Environmental Concerns − P Management − Approaches to Improve P Balance − Management to Reduce P Losses − Summary

P Management - Improve P Balance NPM Program

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

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!

P Management - Improve P Balance Use Starter Judiciously − Recommendation: for corn band apply starter fertilizer if needed (10 lb N, 20 lb P 2 O 5, 20 lb K 2 O) − On soils in the excessively high range for P, avoid starter applications in excess of

P Management - Improve P Balance

− 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 Manage Dietary P Goal: avoid overfeeding P FOLLOW DIETARY P GUIDELINES

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

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

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

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

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

P Management - Reduce P Loss Identify low risk sites − Source and transport – site specific: − P Index: − SNAP-Plus:

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.

Field Crop ID: Orange=cornGreen=alfalfa Yellow=oats(alf. Seed) PI Values: Red=>4Orange=3-3.9Blue=2-2.9Violet=1-1.9 UW Platteville Farm: 2004 Rotation

P Management - Reduce P Loss − Weather predictions − Time of year Consider seasonal limitations to manure applications

P Management - Reduce P Loss − Incorporation of broadcast fertilizer with tillage OR − Subsurface band placement Incorporate P fertilizer

P Management - Reduce P Loss Incorporate manure?? Runoff Dissolved P Losses Source: Bundy and Andraski, 2001 Runoff Dissolved P mg/L Spring Runoff

P Management - Reduce P Loss Incorporate manure?? Total P Losses Spring Runoff Total P load g/ha Source: Bundy and Andraski, 2001

P Management - Reduce P Loss How does manure affect runoff P losses? Surface Applied (not incorporated) -acts as a mulch -provides surface residue cover -decreases erosion -increases soluble P losses (especially on no-till or alfalfa in the winter) Incorporated -increases erosion -decreases soluble P losses Manure applications reduce runoff volumes and soil loss

P Management - Reduce P Loss Use soil conservation practices − Examples − Changes in land management practices (cover crops, diverse rotations, conservation tillage**, contour farming) − Installation of structural devices (buffer strips, diversions, grade stabilization structures, grassed waterways, and terraces ** most widely adopted and easily accomplished

P Management - Reduce P Loss − Reduces amount of runoff − Reduces eroded sediment Use soil conservation practices

Summary − Soil Testing ensures adequate supplies of nutrients for crop production − P Sources = soil, plants, fertilizers, manures, livestock feed, industrial and municipal wastes − P Transport occurs through runoff, erosion and leaching (usually insignificant in WI)

Summary − Eutrophication of surface water is the main phosphorus pollution issue IMPROVE P BALANCE -Follow soil test recommendations -Credit manure P -Use starter only if needed -Reduce P in diet -Increase land base for spreading REDUCE P LOSS -Use PI to determine low risk areas for manure application for manure application -Watch the weather forecast -Incorporate P fertilizer -Use soil conservation practices

Take Home Message Keep P in the field! -for crop use -out of surface water