Author(s)

S. Mishima

Abstract

To evaluate phosphate flow in Japan in 1997, I constructed a framework then estimated and evaluated it. Phosphate input to farmland was 4.3 times larger than output, and the largest in input was chemical fertilizers, 79% of input. Outflow as water-soluble phosphate from farmland was small; therefore, a large amount of phosphate has remained in the farmland soil and has accumulated year by year. Livestock excreta production was about half that of chemical fertilizer, though 38% of livestock excreta was not utilized. Though available phosphate in farmland has been surveyed several times systematically, total phosphate has not been surveyed. Understanding total phosphate resources in farmland and active use of livestock excreta is important for resource management and for reducing environmental risk. 1 Introduction Phosphate is an essential element for crop productio

Keywords