Studies on the Irrigation and the Deep Ploughing : II. The nutriments absorption of upland rice and soybean, and the changes in soil properties

Abstract

In order to know the effects of irrigation, deep ploughing, heavy rate application of fertilizers and their combined treatments on the nutrient uptake by crops and physical and chemical properties of soil, the present studies were carried out. The results obtained are as follows: 1) Generally, the amounts of nutrients absorbed by the upland rice and soybean increased with increasing the rate irrigation, deep ploughing and heavy application of fertilizers, especially the effect of irrigation was most conspicuous. The promotive effects were observed evidently between these treatments one another and the increments of nutrient absorption by the crops were very remarkable with combinations of two or three. 2) By deep ploughing, the soils underlain the top layer, which had very poor physical and chemical properties, were improved strikingly, especially increase of porosity and fertility were observed. Furthermore, it was recognized that the amelioration of acidity, increment in exchangeable bases and so on caused by irrigation were more remarkable in deep soil layer when treated together with deep ploughing. 3) From a stand point of status of nutrient absorption by crops and physical and chemical properties of soil, it was clarified that there was interaction among irrigation, heavy application of fertilizers and deep ploughing