Soil Microbial Activity and Effect of Compost Application on Crop Production

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Sustaining or increasing soil productivity depend in part on soil and crop management practice that maintain or increase soil organic matter. Degradation of soil organic matter is very important to establish reasonable methods of fertilizer and manure application to crop field and preservation of natural environment. The quantitative prediction of carbon dynamics in soil plays an important role in establishment to those methods.The compost application experiments in experimental field of Kyoto University were carried out. The effects of compost application on the yield of forage crops, corn-barley rotation, were examined. The results obtained through experiments and quantitative analysis can be summarized as follows.(1) The time course of carbon dioxide evolution obtained from wet soil incubation experiment under constant temperature (9, 22.5, 37.5 ﾟC) was well approximated by simple model as described below. S = S0 (1 - exp (-k・ t))(2) Using the above equation, Arrhenius' low k = A・exp(-Ea / R・T), characteristic parameters such as S0, k, Ea and soil temperature T, degradation of soil organic carbon under field condition was estimated. The estimated value of soil carbon content were approximately equal to the value of soil analysis at each harvest time.(3) Carbon dioxide evolution was related to soil moisture. Carbon dioxide evolution was maximum at the optimum soil moisture condition(24 to 37 % dry soil weight), and carbon dioxide evolution decreased when soil moisture was more dry or wet than optimum condition.(4) Using the data of soil moisture of experimental field, correction factor was calculated. And then, the corrected value of annual degradation rate of soil carbon decreased at 6 % compared with non-corrected value.