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Studies on humus-concretions in subsoils of paddy fields



Studies on humus-concretions in subsoils of paddy fields



Tohoku Jour Agric Res 3(1): 1-13



Soft black bodies of the size of pebbles are found below the surface of rice fields, at the level of the water table during the drained season, when either the soil or the irrigation water contains much lime. They consist largely of organic matter with Ca, Mg, Al, and Si. They seem to be formed by the anaerobic decomposition of vegetable matter during the growing season, producing acid humins; these are precipitated by reaction with Ca and Mg, and oxidized to a black color by atmospheric oxygen which reaches them after drainage.

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