Effect of Long-Term Application of Ammonium Sulfate, Urea, Composts, and Calcium Silicate on Macroelements and Rice Yields in Paddy Soil = 논토양(土壤)에서 황산(黃酸)암모늄, 요소(尿素), 퇴비(堆肥) 및 규산질비료(珪酸質肥料)의 연용(連用)이 다량원소(多量元素)의 행동(行動)과 벼 수량(收量)에 미치는 영향(影響)

다국어 초록 (Multilingual Abstract)

A study has been conducted since 1954 to elucidate the effects of longterm application of ammonium sulfate (AS), urea, compost, and calcium silicate(CS) fertilizers on major soil nutrients and rice yields in wetland soil. The soil pH in the AS plot become lower than that in the urea plot but had little influence on rice yield. Continuous application of AS and urea with compost and CS raised the soil pH compared with single applications of AS or urea. Soil organic matter content increased yearly in plot with no fertilizer and in those with AS and urea, and increased considerably in plots with compost and CS. Application of compost and CS promoted rice top growth as well as root growth, resulting in increased dry matter. Soil contents of N, $P_2O_5$, Ca, Mg, and $SiO_2$ in the NPK with composts plot increased considerably compared with the NPK plot; however. the exchangeable K content was rather low. Rice growth increased with compost application. which enhanced K uptake, and the coarse texture promoted K leaching. With compost and CS addition, con tents of exchangeable Ca and Mg in the AS plot decreased considerably more than in the urea plot. Probably this was the result of higher Ca and Mg precipitation by sulfate in the AS plot. The re are no significant differences in rice yield between AS and urea plots. With compost and CS treatments, rice yields increased in the AS plot compared with the urea plot. The increase in yield is considered to be the effect of S. which is a constituent of AS.