Application of organic amendments can increase dissolved organic C (DOC) concentrations, which may influence movement of nutrients and heavy metals in soils. The objectives of this study were to investigate the influence of compost sources and application rates on concentrations of soil DOC, NO3-N, and extractable P over 29 months after a one-time application of compost to bermudagrass [Cynodon dactylon (L.) Pers.] turf. Few differences were evident between compost sources for soil total organic C (TOC), DOC, and NO3-N. However, the initial P content of compost sources significantly influenced soil extractable P. Increasing the rate of compost application increased soil TOC initially, but levels remained fairly stable over time. In contrast, DOC continued to increase from 3 to 29 months after application, suggesting that compost mineralization and growth of bermudagrass contributed to DOC dynamics in soil. Dissolved organic C was 98%, 128%, 145%, 175%, and 179% greater 29 months after application of 0, 40, 80, 120, and 160 Mg compost/ha, respectively, than before application. Rate of compost application had less effect on DOC than TOC, as DOC concentrations appeared controlled in part by bermudagrass growth patterns. Soil NO3-N was generally unaffected by compost application rate, as NO3-N decreased similarly for unamended soil and all compost treatments. Soil extractable P initially increased after compost application, but increasing the application rate generally did not increase P from 3 to 29 months. Seasonal or cyclical patterns of TOC, DOC, and extractable P were observed, as significantly lower levels of these parameters were observed in dormant stages of bermudagrass growth during cooler months.
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