Best Management Practices to Minimize Nutrient Losses from Manured Fields Hailin Zhang Oklahoma State University
Pathways of P Transport Inputs Manure Outputs Fertilizer Erosion of particulate P NPK Release of soil P P leaching is small Tile flow Subsurface flow In-channel processes Stream bank and bed erosion/ deposition and biologicalchemical uptake/release
P Sorption Capacity For 3 Soils 300 P Sorbed (mg/kg) 250 200 150 100 50 0 Parsons Smax-289 Clay-30% OC-1.4% Grant Smax-168 Clay-26% OC-0.78% Dalhart Smax-64 Clay-12% OC-0.35% 0 4 8 12 16 20 Equil. P Conc. (mg/l)
Low sorption capacity soil sandy, low clay soil High sorption capacity soil high clay (Al / Mn oxide)
Sharpley et al., 1998
Reducing P Going to Streams & Lakes Manure management Soil Management Reduce buildup of STP (don t apply to soils already high) Time application for lower risk Choose sites for lower risk Remove P with crop Employ other BMPs to Minimize P transport
Manure Management Strategies
Reduce ammonia volatilization Reduce water soluble P Alum Applied to Poultry Litter P. More
CumulativePRunof (kgp/ha) P runoff from normal litter was 340% higher than alum-treated litter 16 14 normal liter alum-treatedliter 12 10 y=1.41x+1.36 2 R=0.97 8 6 4 2 y=0.4x- 0.07 2 R=0.97 0 0 2 4 6 8 10 Time(years) P. More
Runoff P (ppm) Amend litter and soil to reduce P solubility Effect of WTR on Runoff P 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 No WTR WTR Plot 1 Plot 2 Plot Number
Soil Management Strategies
P-Based Manure Application Based on agronomic P requirement Soil test P threshold P Loss (risk) Index (assessment) ratings
N to P 2 O 5 Ratio Plants Litter 4-8 to 1 1 to 1
Soil testing guides where to apply fertilizer and manure 1 / / 2 x / 3 / / 4 / 100 57 30 STP 0-65 65-120 120-250 x 5 / x x x STP x 7 250-400 400+ or no application 6 123 177 x / x Soil Test Phosphorus
Critical Sources of P Loss ~90% of P export comes from < 20% of watershed P loss vulnerability Low (clear)) Medium High
Potential Land Application Problems Fields with sub-surface drainage tiles Fields with highly erodible soils Fields that are snow covered or frozen
Application Equipment Equipment is used for nutrient management not waste disposal Equipment calibration Verify actual application rates Evaluate application uniformity Annual calibration
Buffers Are there no grassed, vegetated buffers between cropland and surface waters? Are they poorly or not vegetated? Is manure applied within 100' of surface water w/o a vegetated buffer?
Vegetative Filter Strips Reduces Surface Runoff Increases Infiltration of Runoff and Nutrients Promotes Sediment Deposition and Filtering Provides Uptake of Nutrients by Plants
Phosphorus Concentration In Runoff (ppm) 7 6 5 4 3 2 1 0 Total Phosphorus Soluble Phosphorus 0 15 30 45 60 75 Buffer Strip Length (ft)
Phytoremediation Plant and harvest high yielding and high P forages It does remove P but it is slow to reduce soil P once it s already very high
Approximate quantities of nutrients removed under grazing and haying systems System Nutrient Removal (lbs/ac) N P 2 O 5 K 2 O Grazing 12.5 7.8 0.9 Crabgrass 223 103 202 Bermudagrass 250 64 216 Both warm and cool season grasses?
Time needed to reduce STP by 100 using plants Time (yeras) 60 50 40 30 20 10 0 2 3 4 5 6 7 8 Time needed to decrease STP by 100 Annual Forage Removal (ton/acre)
Drainage Ditch Management High P water Sorption layer with retained P Drainage layer (sand/perforated pipe) Low P water
Poultry Litter Subsurfer
How it works: Discs open slots Pulverized litter (internal patented mechanism) is delivered to the slot Closing wheels seal the soil surface Can be adjusted to meet a variety of rates Greater accuracy and precision across a range of rates
No litter is left on the surface.
Subsurface band
P load (lbs acre -1 ) Phosphorus Loss in Runoff 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 Broadcast Subsurfer
Amonnia Loss (lbs acre -1 ) Ammonia Loss 9 8 7 6 5 4 3 Broadcast Subsurface No Manure 2 1 0 Maryland Pennsylvania
Summary Animal manure is an excellent nutrient source and soil conditioner Over applying or mismanaging manured fields may result in high nutrient losses Manure can be managed to reduce nutrient solubility A number of BMPs are available to minimize nutrient loss from manured fields.