Phosphorus Cycle, Fertilizer and Organic P Sources. Fundamentals of Nutrient Management Training. August Morgantown, WV. Ed Rayburn West Virginia University Extension Service

Phosphorus P is phosphorus, the mineral essential for energy metabolism and bone formation. P 2 O 5 is the measure of fertilizer plant nutrient. P 2 O 5 = 2.3 x P

Soil phosphorus Total P in surface soils (0.005 to 0.15%) Organic P in soils (50% of total P) –RPO 4 +H 2 O >HPO ROH Soil solution P for optimum crop production 5 to 300 ppb P for algal growth 10 to 30 ppb

Plant available forms of P H 2 PO 4 - pH<7.2 HPO 4 -2 pH >7.2

Phosphorus fixation Reduction in P availability Precipitaion reactions Low pH –Iron and aluminum phosphates (insoluble compounds) Adsorption reaction High pH –Formation of Calcium phosphates (Insoluble)

Phosphorus adsorption Chemisorption Physical electrostatic adsorption Most adsorption on iron and aluminum oxides Kaolinite clay minerals Low pH increases adsorption of P P adsorption higher at high clay content

Converting to Mehlich 1 Phosphorus pH<5.6 Weak Bray P ppm x 0.6 = Mehlich 1 P ppm pH Weak Bray ppm x 0.7 = Mehlich 1 P ppm pH Weak Bray ppm x 0.8 = Mehlich 1 P ppm pH>6.9 Weak Bray ppm x 1.2 = Mehlich 1 P ppm Morgan ppm x 1 ~ Mehlich 1 P ppm

Forage yield response to soil test P.

Fertilizer P affect on forage yield when soils test medium to high in P.

Fertilizer P affect on forage yield when soils test low in P.

Components of nutrient cycling Mass Balance = Import – Export –Import = forage + grain + minerals + fertilizer + rainfall –Export = animal products + crops + run off + erosion + leaching Recycling within farm –Nutrient content of pasture, crop, and supplements –Nutrients excreted by animal vs. removed in product –Recovery of urine and feces –Uniformity of return to area removed from –Location of areas having a net import or export

Nutrient value of pasture, hay, silage, and grains.

Nutrient content of pasture crops in terms of fertilizer nutrients. Pounds/Ton at 90% Dry Matter NP2O5P2O5 K2OK2OCaCO 3 MgCO 3 Pasture, grass Pasture, mm grass Pasture, mm legume Pasture, legume SD

Nutrient content of hay crops in terms of fertilizer nutrients Pounds/Ton at 90% Dry Matter NP2O5P2O5 K2OK2OCaCO 3 MgCO 3 Hay, grass Hay, mm grass Hay, mm legume Hay, legume Hay, small grain Straw corn stalks62773 SD

Nutrient content of silage crops in terms of fertilizer nutrients Pounds/Ton at 33% Dry Matter NP2O5P2O5 K2OK2OCaCO 3 MgCO 3 Silage, corn Silage, grass Silage, mm grass Silage, mm legume194 6 Silage, legume Silage, small grain Silage, sg and leg SD31541

Nutrient content of grain crops in terms of fertilizer nutrients Pounds/Bushel at 85% Dry Matter --- NP2O5P2O5 K2OK2OCaCO 3 MgCO 3 Corn, shell Wheat Oats Barley Soybeans SD

Average nutrient content of manure. Source and FormNP2O5P2O5 K2OK2OCaMgS Poultry (broilers, lb/t) Poultry (layers, lb/t) Dairy (solid, lb/t) Dairy (liquid, lb/1000 gal) Swine (liquid, lb/1000 gal) Horse (solid, lb/t) Adapted from V.A. Bandel Univ. MD Fact Sheet 512. Using Manure to cut Fertilizer Costs

Animal (mineral) vs. fertilizer (oxide) forms of nutrient measurements

CP = 6.25 N P 2 O 5 = 2.29 P K 2 O = 1.20 K CaCO 3 = 2.50 Ca MgCO 3 = 3.47 Mg Conversion from fertilizer nutrient to mineral form.

Nutrient value of milk, meat, and wool

Nutrient value of animal products

Magnitude of nutrient cycling by a 1000 lb. cow.

Magnitude of nutrient removal by a 500 lb. steer.

Magnitude of nutrient removal by a dairy cow making 10,000 lb. milk.

Annual nutrient cycling or removal by different classes of cattle.

Nutrient value of fertilizers.

Phosphate sources triple superphosphate(0-46-0) DAP( ) superphosphate(0-20-0)

Livestock excrete excess P in manure with little in urine.

July 2009 fertilizer prices N from urea $0.50 / lb P2O5 from TSP $0.50 K2O from KCl $0.75

The dollar value of plant nutrients (N, P 2 O 5, and K 2 0) passing through a 1000 pound cow each year is ~ $150 to $250.

Summary : Components of nutrient management Mass Balance = Import – Export –Import = hay + silage + grain + minerals + fertilizer –Export = milk + meat + wool + surface loss+leaching Recycling in pastures and meadows –Nutrient content of pasture –Uniformity over area (or lack of) –Location of areas having a net manure import –Location of areas having a net manure export

Take home lesson: Effective recycling of nutrients in manure is an important way to reduce fertilizer cost and prevent environmental contamination.