Nutrient balance and nutrient use efficiency in Japan

This study aimed to evaluate the reactive nitrogen (Nr), phosphorus (P), and potassium (K) balance and use efficiency as the basics for crop fertilization management, soil fertility management, and indicator for potential of negative environmental impacts from 1980 to 2010. I categorized 70–100 crops listed in past statistics into seven crop categories (paddy rice, upland crops, vegetables, orchards, tea, forage, fodder). Individual documents from a national survey of farmland soil management, conducted six times from 1979 to 2012 by the Ministry of Agriculture, Forestry and Fisheries, Japan, were used to estimate Nr, P, and K application for the seven crop categories as chemical fertilizer and livestock manure. Production of Nr, P, and K were estimated from agricultural statistics and the Food Nutrition Standard. The balance of NrPK was defined as the application less production for the seven crops. Use efficiency of NrPK was defined as the application divided by the production for the seven crops. In general, vegetables and tea received significantly higher NrPK application than paddy rice, forage, and fodder. Forage and fodder NrPK production was significantly higher than for paddy rice and orchard crops. The balance of NrP was larger in vegetables, orchards, and tea than in paddy rice, upland crops, forage, and fodder, although the K balance was not significantly different between the seven crops because of the large variation in the K balance. The use efficiency of NrP was higher in paddy rice, upland crops, forage, and fodder than in vegetables, orchards, and tea because of the lower application and relatively higher NrP production, especially in forage and fodder. Use efficiency of K was higher in upland crops, vegetables, tea, forage, and fodder than in paddy rice and orchards because of the small K production of these crops. Lower application of NrPK would be a simple and easy strategy for crop production and soil fertility management; however, it would be more effective to incorporate crop physiology, nutrient demand, crop quality, soil NrPK condition, and prevention of excess intake of nutrients by crops. These practices would increase crop and soil health and would result in better soil security.