Enhancing Phosphorus Availability in Low-Phosphorus Soils by Using Poultry Manure and Commercial Fertilizer

Phosphorus (P) is an essential element for plant growth and productivity, and lack of available P in soils can severely affect crop yields. Incubation and greenhouse studies were conducted to determine the effect of solitary and combined application of commercial fertilizer P and poultry manure on the soil-available P and plant nutrition of soybean (Glycine Max L. Merr.) in three soils of different chemical characteristics. The soils were low in soil test P (Olsen P), with values of 0.7 mg kg(-1) (Pine canopy sandy clay loam), 4 mg kg(-1) (Faridkot silt loam), and 10 mg kg(-1) (Haibowal sandy loam). Soils were equilibrated for 56 days (incubation study) and 60 days (greenhouse study) with four levels of P equivalent to 0, 13, 26, and 39 kg total P ha(-1) from monocalcium phosphate [Ca(H2PO4) center dot H2O]. Poultry manure was added to one set of each soil at 4.5 Mg ha(-1) (37 kg total P ha(-1)). The combined application of fertilizer P and poultry manure significantly (P < 0.05) increased Olsen P in all soils compared with a separate application of fertilizer P and poultry manure. The greatest increase in soil solution P concentration was observed for the Pine canopy sandy clay loam (150%), followed by the Haibowal sandy loam (56%), and the Faridkot silt loam (28%). Application of poultry manure at 4.5 Mg ha(-1) partially supplemented the P requirement of the soybean crop: 10 kg total P ha(-1) in the Pine canopy soil and 3.7 to 3.9 kg total P ha(-1) in the Haibowal and Faridkot soils. The contribution of fertilizer P and poultry manure to P uptake by soybean was significantly greater in combined than separate treatments. I conclude that in soils that have low amounts of available P, the combined application of fertilizer P and manure may be beneficial to increase P availability to meet crop P needs. However, there is a risk that combined application of fertilizer P and manure in soils that have high soil test P because of historic application of animal manures (especially in the United States and Europe) may lead to greater losses of P to natural waters.