Effects of Organic Amendments and Cultural Practices on Soil Physical and Chemical Properties on Zoysiagrass (Zoysia japonica) Fairway.

Organic amendments can enrich soil fertility and promote soil health. It is unclearly, however, how effects of organic amendments from various sources differ and whether the positive impact resulting from the amendments can be optimized by methods employed in delivering the organic materials to soil. The objective of this study was to evaluate the impacts of various organic amendments delivered by topdressing or topdressing following aerification on soil physical and chemical properties. A two-year field experiment was established on a golf course fairway with zoysiagrass (Zoysia japonica) growing on a native soil (silt loam) in Columbia, MO. Organic amendments applied included an animal waste-based product (AW; Back to nature chicken manure), a sewage-based organic N fertilizer (ON; Milorganite), and a plant byproduct (PB; mustard seed meal), in addition to a synthetic N fertilizer (SN; UMAXX), a synthetic fungicide (SF; azoxystrobin), and an untreated control (UN). All materials were applied by topdressing with sand or topdressing following aerification two times per year (spring and fall) for two years. The same amount of N, approximately 150 kg ha^-1 per year, was added in all treatments with the exception of SF. Soils treated by topdressing following aerification had significantly lower thatch depth and bulk density than topdressing only, which were 19% and 1% less compared to those by topdressing only, respectively. These observed differences from topdressing following aerification treatment were accompanied by elevated soil Ca, Mg, organic matter (OM), and cation exchange capacity (CEC) up to 12%, compared to plots receiving topdressing only. Soil amendments applied did not show statistical differences in soil physical properties evaluated. At one year after the initial treatment application (YAIT), soil organic C to N ratio (C/N) maintained at about 10.5 for both delivering practices. At two YAIT, however, plots receiving topdressing following aerification showed lower C/N, about 90% of that in plots receiving topdressing only. Organic amendments application did not result in changes in soil pH, with the exception of plots receiving AW where soil pH increased by 0.1 unit. Plots receiving AW also had elevated soil P and K levels, which were 9% and 7% higher, respectively, than those in the UC. At two YAIT, little difference in soil NO₃-N was observed among plots receiving different amendments. However, NH₄-N in plots receiving SN delivered by topdressing following aerification was elevated by 43% comparing to UC. This, however, was not observed in plots where SN was delivered by topdressing only. The results suggested that the reduced thatch depth and soil bulk density resulted from topdressing following aerification may have contributed to the increases of some soil chemical properties, such as OM and CEC. More details will be discussed during the presentation.