The 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 (PO₄³⁻) leachate concentrations. Greens were constructed according to the recommendations of the US Golf Association (USGA). Leachates from fertilizer were analyzed for DOC and PO₄³⁻. 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 10-fold greater C content than Nature Safe. Greater DOC from Milorganite more strongly influenced PO₄³⁻ transport than Nature Safe DOC. Concentrations of PO₄³⁻ were correlated with DOC in leachate (r = 0.68, P £ 0.001). Milorganite promoted 15 to 18% greater PO₄³⁻ in leachate than synthetic fertilizer and Nature Safe, with Milorganite PO₄^3−- as high as 2.49 mg L⁻¹. Greater PO₄³⁻ 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 PO₄³⁻ leaching especially on soils with low P sorption capacities.