유기물(有機物)의 시용(施用)이 토양(土壤)의 화학적(化學的) 성질(性質)에 미치는 영향(影響)

Effects of Organic Materials on Soil Chemical Properties

A review was made on the effect of organic matter application on the chemical characteristics of soils such as pH, solubilities of minerals, and cation exchange capacity mainly at flooded rice soils. The review can be summarized as follows: 1. Application of organic material such as rice straw and compost in flooded rice soil leads to a temporary lowering of soil pH at the earlier stage of soil reduction, due to the production of various organic acids and carbonic acid. This temporary lowered pH is replaced with the production of alkaline substances such as ammonia as the reduction of soil proceeds. 2. Incorporation of organic materials intensifies the ferrous iron, dissolving various minerals, virtually to the increase in electrical conductivity of soils. 3. Organic materials also play an important role in dissolving soil minerals through the production of various chelating agents. 4. Application of soil organic matter significantly increases cation exchange capacity of soils. 5. Continuous application of rice straw or compost leads to the increase in soil organic matter content to some extent, up to the level of equilibrium. In soils low in organic matter the equilibrium level is attained with five years continuous application of compost. 6. The manner of chemical fertilizer application influences the accumulation of organic matter applied in soils. Low levels of fertilization lowers the accumulation while high levels of fertilization accerelates the accumulation.