Abstract
The outline of this experiment and its results of: the first 14 years were reported in the previous, paper of this series. This paper deals with the -observation on soil profile made in 1958 and the resulfs of soil analyses on the physical and chemical properties made in 1958 to 1960.
1. Excavation of the soil profile revealed that a clay pan derived from shale was underlying at the -depth of about 40 cm, which restricted root penetration below this layer.except for a few large roots. In the soil profile to 40 cm deep, deeper root distribution and more fine roots were found in the plots recieving larger amount of green manure.
2. Physical properties of soil such as porosity, soil moisture retention, and development of soil. aggregates, were improved by the application of .green manure, especially in the 75% and 100% plots.
3. Humus content in the surface layer (0_??_7cm) was 5.66% (dry soil base) in the 100% plot, and 1.84% in the 0% plot. Humus has been accumulated in the plots where 50% or more of the fertilizer elements were applied with the green manure, and high humus content was accompanied with high nitrogen content.
4. Soil reaction in the 0% and 25% plots was strongly acidic, while the soil in the plots recieving ample supply of green manure was nearly neutral in its reaction.
5. Cation exchangeable capacity and total exchangeable cation content of the soil were increased in proportion to its organic carbon content.
6. It may be concluded that the above mentioned changes in the soil due to the application of green manure enhanced the development and activity of roots and also increased the growth and yield of citrus trees. These effects were especially conspicu ous in the 75% and 100% plots.
