Influence of Four Essential Elements, N, P, K and Ca on Decomposition of Organic Matter in Soils.

Abstract

1) Rate of decomposition of filter paper and rice straw in soils from Kyoto University Experimental Field and 'Uji' Tea Experiment Station was investigated, and found that the rate has a close relation to nitrogen and the reaction of the soils in both dry-farm and paddy field. The rate is increased greatly by addition of N while P and K have no appriciable influence. The rate in the soil from Kyoto Univ. which is neutral in reaction was much greater than that in 'Uji' soil of which reaction was strongly acid. But the neutralization with lime in case of the latter increased the rate. 2) While in the previous cases, the application of P and K had no appreciable influence on the rate of decompositis, on other soils from 'Siga' Agr. Experiment Station which received no P, and K for continuous years, the rate was increased markedly by the application of P and K respectively. From these results it is stated that the rate of decomposition of organic matter in the soils which lack N, P and K is increased by the addition of these elements, and where the reaction is acid, it is increased by the neutralization of the acid by Ca, in the same manner as the plant growth.