Evaluation of organic turfgrass management and its environmental impact by dissolved organic matter
Incorporation of organic fertilizers/amendments on turfgrass management has been, and continues to be, a popular strategy of integrated pest management (IPM) program to reduce environmental impacts by pesticide and nitrate leaching. Most of the research on organic fertilizers for the turfgrass industry has focused upon disease suppression, improving soil physical, chemical and biological properties, and the fertility effect on high-cut turfgrass. However, little information has been reported on the response of highly maintained golf turfgrass, such as common on golf courses. The current research studied the effects of organic fertilizer as a sole source on turfgrass performance on highly maintained golf turf and its short-term effects on total soil microbial dynamics on different soil profiles. In addition, environmental impact by organic fertilizer derived dissolved organic matter (DOM) on pesticide sorption and transport in soil was also investigated.
Four natural organic fertilizers were evaluated in this study which includes Milorganite (6-2-0), NatureSafe (8-3-5) and SoylMicrobial (F as flowable and G as granular, 14-1-1) and one synthetic organic fertilizer Scotts (29-3-4). In soil microbial dynamics study, application of all natural organic fertilizers increased soil bacterial populations within 4 days after fertilizer treatment (DAT) while little or no effect with the synthetic organic fertilizer was observed on all three soil profiles for the growth chamber experiment. Similar results were observed for the 2 year field trials, however, only the SoylMicrobial (F) fertilizer treatment increased total bacterial populations at 2nd and 4th DAT.
In turfgrass response under organic fertilizer application experiment, weekly applications increased clipping an average of 43% compared with bi-weekly applications. Overall, native soils provided higher clipping yields than USGA sand and mixed soil profiles. SoylMicrobial provided sufficient N for acceptable turfgrass growth and Milorganite was ineffective as a sole turfgrass fertilizer. These results suggested that selected natural organic fertilizers can be used as a sole source for turfgrass fertility and the application rates and frequencies need to be adjusted for the different soil profiles.
Batch equilibrium techniques were used to evaluate relative effects of organic fertilizer-derived DOM on sorption transport of three organic chemicals (2,4-D, naphthalene and chlorpyrifos) in soils. Sorption capacity was significantly reduced with additional DOM in solution for all three chemicals. The higher the concentration of DOC in solution, the more sorption was reduced. Column experiment results were consistent with batch equilibrium results suggesting that organic fertilizer-derived DOM might lead to enhanced transport of applied chemicals in soil. Results also suggested that organic fertilizers should not be applied on turf directly after pesticide application, which would reduce the impact of organic fertilizer-DOM facilitated transport of applied pesticides.
0768: Environmental science