Fertilizer Efficiency and Nitrogen Behavior after Application of Rural Sewage Sludge-rice Husk Compost to Brassica rapa var. peruviridis

Abstract

In order to investigate fertilizer efficiency of rural sewage sludge-rice husk compost (hereinafter, SH compost) and the behavior of nitrogen after application, Komatsuna (Brassica rapa var. peruviridis) cultivation was conducted with three different rates of SH compost application.
Fertilizer efficiency ratio of SH compost was 58% to chemical fertilizer. This suggested SH compost was considered to be readily available fertilizer like poultry compost. However, nitrogen recovery rate decreased as the amount of SH compost application increased.
The measured δ¹⁵N of Komatsuna leaf increased as the amount of SH compost application increased. Nitrification, denitrification and ammonia volatilization in soil might increase the δ¹⁵N of Komatsuna leaf in this experiment. The reason of increase in δ¹⁵N was thought to be not nitrification but the changes of emission rate of N₂O or NH₃ to the atmosphere since nitrogen recovery rate decreased with increase in the amount of SH compost applied.