Phosphorus Source Effects on Soil Organic Phosphorus: A 31P NMR Study

The nature of organic phosphorus (Po) in animal waste and in soil is important from both plant nutrition and environmental perspectives. The objectives of this study were (1) to monitor the nature of Po in different animal wastes and biosolids using solution state P-31 NMR spectroscopy and (2) to understand the nature of Po as affected by crop P removal in soil amended with different animal wastes and biosolids under greenhouse conditions. Two types of stockpiled cattle (Bos taurus) manure (CM1 and CM2), solid turkey (Meleagris gallopava) litter (TL), solid hog (Sus scrofa) manure (HM), and aerobically digested biosolids (SS) were used. Two kg of Wabash silt loam soil was amended with 0 or 150mg P kg(-1) from the P sources. Seven harvests of corn (Zea mays L.) were collected, each 35 days after sowing. Organic P was extracted with 0.4M NaOH from soil samples collected before cropping and after the seventh harvest, as well as from each P source. P-31 NMR analysis suggested that sugar phosphomonoester was present in all P sources and was the dominant constituent of both CM1 and CM2. Phosphomonoester was detected in large amounts in TL, HM, and SS. Prior to crop P removal, the application of all P sources caused the relative content of sugar phosphomonoester to be greater than the control. Crop P removal resulted in reductions in the relative content of sugar phosphodiesters and phosphodiester in CM1- and CM2-amended soils, respectively. Phosphomonoester was also decreased in TL-, HM-, and SS-amended soils in response to cropping.