INFLUENCE OF SOIL AGGREGATION ON PLANT GROWTH

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Abstract
A greenhouse expt. was performed to investigate the relation between plant growth and soil structure as found by aggregate analysis. Three forms of aggregate sizes were prepd. by crushing the clods of a heavy, red clay soil that has naturally very coarse aggregates. The crushing did not induce chemical or textural changes in the soil treated, so far as it was tested. The size of aggregates was the only independent variant. Wheat was grown in greenhouse pots. The variously aggregated soils produced highly significant differences in yields. The coarsely aggregated soil produced much better plant growth than did the finely aggregated soil. As a possible cause of the reduced yields in the finely aggregated soils, insufficient supply of oxygen is suggested. Presumably the low supply of oxygen influenced at least 2 processes: it diminished the ability of roots to absorb nutrients, and it depressed the supply of some available nutrients to the growing plants. Some evidence is given in support of thison. Structural changes of the soil may considerably influence results of fertilizer tests.