Results of variable-rate nitrogen fertilization of winter wheat based on soil fertility and yield map

Based on 18 m×18 m grid-sampling of Alkali-soluble soil nitrogen and yield map in 2001, variable-rate nitrogen fertilization prescription was produced for winter wheat and examined in farmland in 2002. Compared to uniform nitrogen fertilization, variable-rate nitrogen fertilization caused slightly lower yield and higher coefficient of variance of yield. Ear density in variable-rate zone is approximately equal to that in the uniform fertilization zone, but has lower coefficient of variance. Number of grains per ear in variable rate zone is less than that in the uniform fertilization zone, and has a higher coefficient of variance. Both grain weight in variable rate zone and its coefficient of variance are higher than those in the uniform fertilization zone. Grain protein content in variable rate zone is slightly higher than that in the uniform fertilization zone, while its variability is also higher. Economical benefits of fertilization in variable rate zone are smaller than those in uniform zone. Soil nitrate concentration in variable rate zone after the wheat season is much lower than that in the uniform fertilization zone, and the risk of groundwater pollution by soil nitrate is reduced.