Spatial dependence of nutrients in N, P and K fertilized forest soil

摘要

Experimental semivariograms may be used to characterize the spatial dependence of nutrients in a forest soil. The information is needed to understand the spatial extent of the interaction of fertilizer nutrients with other soil chemical properties. Data were obtained from a field experiment designed to study the response of loblolly pine (Pinus taeda L.) to applied N, P and K utilizing a plot area of 10m X 10m. One year after fertilization, soil samples were collected at two depths, 0-15 cm and 15-30 cm at a one-m grid interval from all three replications. The samples were analyzed for pH and resin extractable P, K, Mg, and Ca. Coefficient of variation (CV) was highest for P (75 percent), lowest for pH (4 percent) and ranged between 17-25 percent for K, Mg and Ca for the 0-15 cm depth. The CV value was higher for the 15-30 cm depth for K (40 percent), and lower for P (54 percent) and Mg and Ca (12 percent) compared to the 0-15 cm depth. Experimental semivariograms were derived for each depth and property. Directional dependence (anisotropy) was observed for pH, Mg, and Ca at the 0-15 cm depth. For the 15-30 cm depths, K, Ca, and pH showed anisotropy. Differences in spatial structure with lag distance, direction and soil depth for the different nutrients studied were attributed to fertilizer rate, plant uptake and vertical movement of nutrients.