Publisher's Synopsis
Excerpt from Some Relations of Organic, Matter in Soils: A Thesis Presented to the Faculty of the Graduate School of Cornell University for the Degree of Doctor of Philosophy
In a comparison of 22 rotation plots no distinct relation has been found between the composition of the soil and the nature of the rotation. In a long cultivated field the till was found poorer in humus, nitrogen and organic carbon than the lacustral clay. The amounts of the above three constituents found in any of the plots depend more upon the relative proportions of the two types of soil occurring on the plots than upon the previous treatment.
The longer the fields have been kept in grasses mown for hay, the less has been the change in composition of the soil. Continuous bare cultivation. Along tree rows has caused greater losses than the alternation of fallow and crop in the adjacent fields. The extreme loss of nitrogen, humus and organic carbon in 25 years is about one-third of the amounts originally present in the prairie.
Bradley (1912) conducted pot experiments from which he pointed out that the nitrogen loss was appreciably reduced by legumes.
Mooers, Hampton, and Hunter (1912) reported that the loss of nitrogen was appreciably greater on limed plats than on unlimed plats, and that the effect extended below the depth of plowing. These investigators stated also that there was an increase in percentage of humus on the unlimed sections.
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