Yield response and economic analysis of fertilizer application in maize    grown in North China Effects of Nutrient Expert Recommend Fertilization on Yield and Fertilizer Efficiency of Summer Maize in Fluvo-Aquic Soil Effect of ecological intensification nutrient management on the yield and nitrogen use efficiency of spring maize Approach and decision support system based on crop yield response and agronomic efficiency Studies on recommended fertilization methods of summer maize in different fluvo-aquic soil texture