Changes in soil available-nutrient stores and relationships with nutrient balance and crop productivity in Japan

Abstract To relate short-term nutrient balances with long-term changes in soil fertility, we compared soil available-nutrient stores with fertilizer application, crop productivity, and nutrient balances. Stores of nitrogen (N: quantity of available N), phosphorus (P: quantity of Truog-P), and potassium (K: quantity of exchangeable K) in the topsoil were calculated five times from 1979 to 2003. In each survey, nutrient inputs by fertilizer, manure, and soil amendment and output by crop removal were calculated. The arithmetic average was calculated for seven crop groups [(paddy rice, Oryza sativa L.), upland crop (wheat, Poaceae triticum L., etc.), vegetables (radish, Raphanus sativus L. etc.), orchards (orange, Malus pumila Mill. etc.), tea (Camelia sinensis L.), forage (Dent corn, Zea mays L. etc.), fodder (timothy, Pheleum pratense L., etc.)] on 16 groups of soils. In spite of large changes in the N balance and in manure N input, available N was relatively constant during the five surveys both within and...