Soil Dynamics and Nitrogen Absorption by a Natural Grassland under Cow Urine and Dung Patches in an Andisol in Southern Chile

The objective of this study was to assess N dynamics in the soil, and the response in regard to dry matter yield (DM yield; kg.DM.ha(-1)), N yield (g.N.m(-2)) and N concentration (g.N.kg(-1) DM) under urine patches and dung pats and in the affected zone of the grassland soil over 304 days. The amount of N under the urine and dung patches increased until day 10 and then started to decrease until the end of the experiment, reaching control treatment levels. The DM yield in the urine patch zone and the 0-10 cm zone around the dung pat was higher than in the control treatment throughout the evaluated period, while in the 0-30 cm zone around the urine patch and the 10-20 cm zone around the dung pat the DM yield was negatively affected by the application of excreta. The maximum accumulated N yield was up to two times higher than the control in the 0-10 cm zone of the dung pat, while the mean concentration of N throughout the period was 42% higher than the control for the "urine patch" zone and 47% higher in the 0-10 cm area around the dung pat. The total absorbed N was 19% and 15% for urine and dung excreta, respectively. Further research is needed to explain the variables that might affect the results obtained, and it is necessary to evaluate the botanical composition as a factor that contributes to this effect.