Long-Term Use of Compost for Soil Improvement and Increased Rice Yield in Irrigated Areas

Abstract

Betweem 1977 to 1984 a study was made to examine the long-term effect of five rates of application of straw compost, zero, 160, 320, 480 and 960 kg ha-1 in combination with N:P:K chemical fertilizer at the rate of 0.96: 0.64: 0.0 kg ha-1, on teh chemical properties of paddy soil and the yield of a non-photosensitive rice variety. The study was conducted on a medium fertility Saraburi clay soil in Suphanburi province of Thailand.
In the first phase of the study, 1977 -78, the thighest rice yield and highest returan resulted from teh use of chemical fertilizer alone; there was no recorded difference in in teh chemical properties of teh soil between the chemical fertilizer treatment and the compost teatments. In the second phase, 1979-1982, wet-season and dry-season fertilizer treatment and the compost treatments. In the second phase, 1979 - 1982, wet-season and dry-season sowing of rice were examined. With dry-season sowings there was a trend of higher yields with compost applied at a rate of 320 kg ha-1 and above, when compared with chemical fertilizer alone; the yield increase was greatest with compost applied at a rate of 960 kg ha-1 in teh sixth year of application. With wet-season sowings there was no significant yield difference between the use of chemical fertilizer and compost. Changes in soil chemical properties were recorded for applications of compost at rates of 320 kg ha-1 and above, for which there were increases in organic matter, phosphorus and potassium contents, when compared with the use of chemical fertilizer or the lower rate of compost. The changes in the soil chemical properties were greatest with the highest rate of compost application. In the third phase of the study, 1983 - 84, the residual effects of the use of compost were studied. The residual effects of the compost application were apparent in each season of production for each compost application rate.