Leaching of phosphorus fractions following manure or compost application

Phosphorus (P) leaching in manure-amended soil can be influenced by the P fractions added when manure or composted manure is applied. This study was conducted to determine leaching of different P fractions following beef cattle feedlot manure or compost application. Manure and composted manure were applied to meet the nitrogen (N) or P needs of corn (Zea mays L.) for either a one or two-yr period. Fertilized plots and unfertilized control plots were also used. The P-based treatments also received additional N fertilizer. Soil P fractions were determined for various soil depth increments. After 4 years of manure and compost applications, leaching of plant-available P was observed to a soil depth of 30 cm. The differences among treatments for total and inorganic P were significant only at the 0 to 15cm soil depth increment. Greater concentrations of total, available, and inorganic P fractions were observed for the N-based manure and compost treatments as these management strategies received more P than P-based. More than 70% of beef cattle manure or composted feedlot manure P was inorganic. Water-soluble P was a small fraction of total P in beef cattle feedlot manure or composted manure (<13%). Leaching of plant-available P following manure and compost applications can pollute the ground water if P comes in contact with ground water, especially in areas with shallow and/or fluctuating ground water and in areas with till drainage.