31P Solution NMR on Wisconsin Biosolids.

Losses of phosphorus (P) from agricultural fields are still contributing to eutrophication of waterways. Over the years many studies have investigated various fertilizer, manure, and biosolid impact on soil test P and runoff P losses. However, much more can be learned by investigating the forms of phosphorus in the organic (manure and biosolid) sources. This research seeks to elucidate differences found between six Wisconsin biosolids (Fort Atkinson, Delafield, Brookfield, Mukwonago, Whitewater, and East Troy). These six biosolids have been previously studied using soil incubations and greenhouse studies. The current study used ³¹P solution NMR to investigate organic P bonds in the six biosolids. Spectra were obtained using a JEOL 400YH NMR with a 5mm probe. Biosolids were extracted with 0.25M NaOH plus 0.05M EDTA followed by centrifugation, filtration, and lyophilization. The pellets were frozen until NMR analysis at which time they were redissolved with deuterium, the extracting solution, and 10M NaOH. Each biosolid sample was run on the NMR at room temperature (approximately 21-22^oC) within 12 hours of redissolving using the following experimental parameters: 90 degree pulse, 0.68s acquisition time, 4.32s pulse delay, with 5,800-48,000 scans. Initial spectra indicate that most of the P in all of the biosolids is orthophosphate. Other peaks common within the biosolids appear to be phosphate monoesters and diesters. The Fort Atkinson biosolid was the only biosolid studied that had a pryophosphate peak. Fort Atkinson was also the only biosolid that lacked the monoester and diester peaks. This may help explain why application of Fort Atkinson biosolid resulted in higher levels of Bray P in the soil and also high total P concentration in the plant in soil incubations and greenhouse studies done previously (even though all amendments were added at the same total P rate). Quantification of these P forms is in process.