Phosphorus and Phosphorus Management Outline Introduction P Sources

Phosphorus and Phosphorus Management

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

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

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 P 1, Mehlich III, Olsen

Introduction P-Crop Need Soil test P, ppm Crop Optimum No response Alfalfa 18 -25 >35 Corn 15 -20 >30 Soybean 10 -15 >20 Medium and fine-textured soils, Bray P-1 test.

Introduction P Forms AS RELATED TO CROPS, SOILS, AND FERTILIZERS − Inorganic P − Organic P − Fertilizers, soluble P − Manure, plant/leaf residues − PO 43 -, HPO 42 -, H 2 PO 4 - − Inositol phosphates, nucleic acids, phospholipids − Immediately available − Slowly available (needs to be mineralized to inorganic form)

Introduction P Forms AS RELATED TO CROPS, SOILS, AND FERTILIZERS − Soil Test P − − − estimates plant available P usually Bray P 1 (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

Introduction P Forms AS RELATED TO WATER QUALITY − Particulate P (PP) − − − Soluble P (SP) − − − definition: P bound to eroded sediment or organic matter also called sediment-P 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

Introduction P 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)

Introduction P Cycle

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

Introduction P Reactions in Soil What happens when fertilizer or manure P is added to soil? − Adsorption and Desorption − Clays, Fe and Al oxides, organic matter (inorganic P) − Precipitation/Dissolution − − Acid soils – Fe, Al, Mn compounds dominate Alkaline soils – Ca compounds dominate 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 1 ppm (Leikam, 1992) − Time is needed to raise OR lower STP

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

P Sources Soil Form Total Soil Test P (agronomic) Soil Solution Concentration (ppm) 400 -1500 20 -50 0. 01 -0. 30 P occurs naturally in soil (but usually in very low concentrations)

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: − − Monoammonium phosphate: NH 4 H 2 PO 4 Diammonium phosphate: (NH 4)2 HPO 4 Triple superphosphate: Ca(H 2 PO 4)2 Easily soluble to runoff water (if rain comes shortly after application) N-P 2 O 4 -K 2 O 11 -48 -0 18 -46 -0 0 -46 -0

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)-- Phosphate Potash Surface Incorporated (P 2 O 5) (K 2 O) ---Solid-----lbs/ton--- Dairy Beef Swine Chicken 3 3 7 20 4 5 9 24 3 5 6 30 7 9 7 24 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 www. milorganite. com

Outline − − − Introduction P Sources P Transport − Runoff and Erosion −Environmental −P Management −Summary Concerns − 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 (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 P Management − Summary − − − Point/Non. Point Pollution Urban/Agricultural

Environmental Concerns Eutrophication − 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?

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 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.

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. 160 320 120 60 45

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

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 10 -20 -20

P Management - Improve P Balance

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

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

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 Source P LOSS Transport

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

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=corn Green=alfalfa Yellow=oats(alf. Seed) PI Values: Red=>4 Orange=3 -3. 9 Blue=2 -2. 9 Violet=1 -1. 9 UW Platteville Farm: 2004 Rotation

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

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

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

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 Incorporated -acts as a mulch -provides surface residue cover -decreases erosion -increases soluble P losses (especially on -increases erosion -decreases soluble P losses (not incorporated) no-till or alfalfa in the winter) 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 Use soil conservation practices − Reduces amount of runoff − Reduces eroded sediment

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 -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