Influence of Dissolved Organic Carbon from Natural and Synthetic Fertilizers on Phosphate Leaching from a Sand‐Based Golf Green

For intensively managed golf greens, organic fertilizers are recommended as an alternative to synthetic fertilizer to reduce nutrient contamination. Dissolved organic C (DOC) strongly enhances solute mobility. Golf greens were established as ‘Penncross’ creeping bentgrass ( Agrostis stolonifera L.) sod to examine two commercial organic fertilizers, Milorganite and Nature Safe, compared with synthetic fertilizer and their influence on DOC and phosphate (PO 4 3− ) leachate concentrations. Greens were constructed according to the recommendations of the US Golf Association (USGA). Leachates from fertilizer were analyzed for DOC and PO 4 3− . Fertilizers were applied as three applications at 50 kg N ha −1 in July, September, and October of 2006. Total P applied was 24.2, 21.5, and 11.2 kg ha −1 for Nature Safe, Milorganite, and synthetic fertilizer, respectively. Dissolved organic C from Milorganite in the fertilizer was 2.4 vs. 0.9% for Nature Safe, with the DOC extract from Milorganite containing 2.7‐fold greater C content than Nature Safe. Greater DOC from Milorganite more strongly influenced PO 4 3− transport than Nature Safe DOC. Concentrations of PO 4 3− were correlated with DOC in leachate ( r = 0.68, P ≤ 0.001). Milorganite promoted 15 to 18% greater PO 4 3− in leachate than synthetic fertilizer and Nature Safe, with Milorganite PO 4 3− as high as 2.49 mg L −1 . Greater PO 4 3− in leachate, with Milorganite having 13% lower total P than Nature Safe, can be attributed to Milorganite's 2.7‐fold greater DOC content. The results suggest that DOC from organic fertilizer and their chemical properties may increase PO 4 3− leaching especially on soils with low P sorption capacities.