2021 Volume 2021 Issue 6 Pages 1-9
Soil organic matter (SOM) is a heterogeneous organic mixture, the half is constructed by organic carbon. Organic matter incorporated to soil is degraded into SOM by soil microbe. SOM increases cation exchange capacity (CEC), namely nourishment retentivity of soil. SOM contributes to form aggregates, and improves drainage characteristics and water retentivity of soil. Because soil microbe degrades SOM and increases, biomass nitrogen which soil microbe holds increases when there is much SOM. Biomass nitrogen is probably correlated with soil nitrogen. However, the increase of biomass nitrogen is accompanied with decrease of SOM. The amount of SOM is decided by the amount of organic matter supplied to soil and the amount of organic matter degraded by soil microbe. The means to supply more organic matter to soil are shifting, continuous supply of compost etc. The degradation of SOM is promoted in the rotational paddy field, soybean cultivation etc. Both of non-flooding in paddy field and soybean cultivation are the treatments to promote degradation of SOM, and the soybean cultivation in rotational paddy field probably degrades SOM remarkably. To use biomass nitrogen and maintain SOM, it is suggested that more amount of organic matter must be supplied to soil than the amount of degradation by soil microbe. Continuous application of organic matter Summary e.g., compost is probably effective for maintenance of SOM.
