Physical Properties of the Soil in Relation to the Alternate Usage of Land for Lowland and Upland Crops

Abstract

In this report, the results of the authors' studies on the changes in physical properties of the soil of fields due to alternate conversion of it into upland vs. lowland conditions, togetherwith the effects of these on the growth and yields of the crops cultivated, are dealt with. The soil of a paddy field continually cropped with paddy in summer every year was simultaneously examined for comparison in the study. 1. The outline of the results are given briefly in the tables 5∼11. 2. On a field converted from an irrigated paddy field into upland condition, the following facts were observed : (1) Soybean growth and its yield in the first year after conversion were found considerably good, while in the succeeding years the yield decreased gradually. (2) Red clover yielded rather poorly in the first year, but gave a remarkably higher harvest the next year. (3) Sweet potato yields were also lowest in the first year, being improved however through the succeeding years gradually. (4) The yield of wheat was higher on the converted field than that on the ordinary paddy field. 3. The growth and yields of paddy crops on lowland fields reconverted from upland condition were found better, especially in the first year, than those on ordinary paddy lands under continual cropping of paddy in every year's summer. The difference in physical properties of soil between the converted and non-converted lowland fields was conspicuous in the first year after conversion, but it became slight in the third year.