Effects of Tillage and Fertilization Rate On Stargrass Pasture Yield and Quality.

A common management practice for dairy farms in the San Carlos region of Costa Rica includes utilization of stargrass (Cynodon nlemfuensis) pasture under heavy grazing pressure. Previous research has shown mineral deficiencies in cattle from this region that may be linked to poor pasture quality. At our research site in Aguas Zarcas, Costa Rica, redoximorphic features beginning at 8 cm below the soil surface indicated serious soil compaction due to cattle traffic; therefore, we hypothesize that compaction may be impeding forage production by diminished root growth and nutrient uptake. The objective of this one year study was to determine if soil physical properties are limiting forage productivity. Nine stargrass pastures with three intensities of grazing pressure were studied to assess the effect of tillage and fertilizer rate on forage quality and yield. Each pasture was divided in half with deep tillage (35 cm) applied to one subplot and no tillage treatment on the other subplots. Each subplot was further divided into three fertilizer treatments; no fertilizer, 50% of the recommended fertilizer rate, and the recommended fertilizer rate. Soil bulk density was measured at three depths before tillage and one month after tillage. Bulk density samples were taken at the soil surface, 8 cm, 18 cm, and measured 0.5803g/cm³, 0.6877 g/cm³, and 0.6744 g/cm³ for the three depths respectively. There was no statistical difference between treatments. Bulk densities were measured throughout the subplots and may not have been taken within the tilled zone. Additionally, forage yields averaged 3420 kg/ha for the tilled plots and 3880 kg/ha for the control and were not statistically different. Tillage destroyed the forage within the treated area and required re-growth which may have temporarily altered results. No difference was indicated with fertilizer application within all treatments.