Soil testing and fertilization indices for major grain and oil crops in Fujian Ⅲ. models and recommendations for regional fertilization

Three regional fertilization models for the "high","medium" and "low" soil fertility grades were established based on 227 field tests on the NPK fertilizer efficiency for the grain and oil crops.Representative model analysis showed that 65.7% of the 35 regional fertilization models were typical.The boundary yield derivative method was used to recommend optimum application rate for the typical models.The Monte Carlo method was applied for non-typical models.The results showed that the average maximum N application rate for the early and the late rice in Fujian was 162 kg•hm-2 with an N P K ratio of 1:0.36:0.72,while the average economic N application rate was 122 kg•hm-2 with an N P K ratio of 1:0.32:0.65.The N P K application rate for the rice in the mountainous area was higher than in the coastal area.The recommended N application rate for the mid-reason rice was 206 kg•hm-2 with an N P K ratio of 1:0.38:0.80.The economical N application rates for sweet potatoes,potatoes and peanuts were 134 217 and 107 kg•hm-2 with N P K ratios of 1:0.47:1.40,1:0.37:1.00 and 1:0.50:0.98,respectively.It is apparent that considerable differences exist in the appropriate fertilization for soils of different fertility grades.