In order to compare the effects of different soil managements on the growth and yield of Satsuma orange trees, and on the physical and chemical properties of soil, field experiments were conducted for 10 years at the Ehime Fruit Tree Exp. Sta.
1. One of experiments was started in 1952 with 4-year-old trees grown on the sloping diluviatic land. The tree growth estimated from the volume of tree crown in the 10th year, was superior both under the bur clover sod and under the orchard grass with partial clean cultivation, then medium both under the wheat straw mulch and under the weed sod, and inferior under the clean cultivation. The total yield of fruit was best under the bur clover, then better under the weed, and bad both under the orchard grass and under the straw as same as under the clean cultivation.
2. Humus content and pore space in the soil increased markedly both under the bur clover and under the straw than under the clean cultivation. The trend extended deeper in the subsoil under the bur clover than under the straw. The pH and exchangeable Ca and Mg levels in the soil had the tendency to rise up greatly under the bur clover. The exchangeable K content of the soil was increased under the straw, though it was not closely related to the K content of leaves.
3. In the 7th year, nitrate nitrogen content of the soil was greatest under the bur clover, followed by the straw and the clean cultivation in the order. It was, however, less under the bur clover than under the clean cultivation, if the sod was not frequently mowed. Mineralization of soil nitrogen was most active in either surface soil under the sod or mulch. The N content of leaves, however, had no connection with the total inorganic or nitrate nitrogen content of the soil.
4. In the other experiments of 1952-1961, 18-year-old trees grown on the flat field, and on the terraced field were used. The effect of the hay mulch was observed with the former, and that of the weed sod with the latter. As the results, no distinct difference of fruit yield existed between the clean cultivation and these two soil management systems in the first 5 years, while in the second 5 years these two systems were slightly superior to the clean cultivation.