Spatial variability of soil nutrients and sitespecific nutrient management in the P.R. China
Preliminary studies on the spatial variability in available nutrient content in agricultural fields under both large scale and small scale operation in China were conducted, and the different technical approaches to realize site specific nutrient management developed. Results indicated that significant spatial variability of all essential plant nutrient exist in different operating systems and at various scales. Under small scale operation within the family responsibility system, in which each farmer's family is assigned to operate one or several small field plots with the field size normally less than one hectare, the large spatial variability of soil nutrients was mainly attributed to the fertilizer history of individual farmers, diversity of crop types and varieties used in relatively small scale field management. Significant correlation was found between crop yields and available soil nutrient levels at the corresponding sites in the field. Based on the understanding of the nature of spatial variability of soil nutrient availability in China, and with the purpose of increasing profitability and sustainability of crop production, a site-specific soil nutrient management strategy is proposed. Related techniques and agricultural services are discussed, including soil testing and fertilizer recommendation, farmers' plot specific or regional specific fertilization approaches and related services at national and regional levels. (C) 2002 Elsevier Science B.V. All rights reserved.
spatial variability site specific nutrient management precision agriculture