Studies on Soils in Transferring Cultivation of Paddy and Upland Field (Part 2) : Properties Concerning with Soil Structure and Nitrogen

Abstract

The purpose of our studies is to investigate the reasons why the crop yield in regions where a transferring cultivation between paddy and upland fields is practiced, is always greater than that in a region where the rice plant is the only crop. Samples of soil are four different types; peat, muck, clay and sandy soils as the same in Part 1. Permeability and temperature of soils, content of FeO, base exchange capacity and content of total and organic nitrogen were determined. The following results were obtained. 1) Permeability of the soil in the transferring fields is greater than that in the one crop paddy fields, because the better soil granular structure is made in the transferring cultivation field. Almost no difference of temperature was between two soils, the paddy field and the transferring cultivation field as shown in Table 3. 2) Content of FeO, total, nitrogen and base exchange capacity, in May, are higher in the transferring cultivation field than in the paddy field. Content of easily decomposed organic nitrogen, in July, has the same result. These results are given in Table 2,4,5 and 7. 3) Contents of NO_3-N in May and NH_4-N in July and September were measured. Rate of availability of N to the rice plant in the transferring cultivation field is more or less slower than in the one crop paddy field, but the efficiency of N is higher than in the one crop paddy field. 4) The reason why the yield of rice plant in the transferring cultivation field is greater than the paddy field, will be explained as that primarily physical soil structure is good for the rice plant, and secondarily efficiency of available N becoms higher.