Spatial Variability of Soil Nutrients and Crop Response to Balanced Fertilization in a Rice Production Area under the Collective Contract System

This study was conducted to determine spatial variability of soil nutrients and crop response to balanced fertilization in a 76.5 ha rice production area of Jiangchuan farm in Heilongjiang Province using traditional statistics and geo-statistics.The results showed that soil nutrient limiting factors were N,P,K and Zn in the study area.Significant differences in contents of soil nutrients among 9 fields were found under three grid-sampling scales(50 m×50 m,100 m×100 m and 150 m×150 m) .Whereas insignificant differences in contents of each nutrient in soil were observed under the three grid-sampling scales.Distinct spatial distribution similarity for each soil nutrient under the three grid-sampling scales was found with relatively high contents in some areas of the study area and relatively low contents in other areas,indicating that status of main soil nutrients under the collective contract system can be evaluated on 150 m×150 m grid-sampling scale,and it was technically feasible to develop regionalized N,P,K and Zn nutrient management at the level of the field in this study area.Regionalized balanced fertilization techniques for high-yield rice production in the study area were developed based on the regionalized soil nutrient GIS maps and a computerized fertilizer recommendation system.The balanced fertilization techniques increased rice yield,income and nitrogen recovery rate by 4.3%-11.2%,779-1 532 RMB Yuan/ha and 12.6-14.0 percentage point,respectively.