Abstract
The ability of roots to penetrate into consolidated subsoil was examined by the field and pot experiments using various kind of tropical leguminous plants. The results revealed that Pigeon pea (Cajanus cajan L.) was the most penetrative and effective in improving the compacted subsoil. Its characteristics are summarized as follows:
1) The growth rate of Pigeon pea was so high, and the roots could penetrate deeply into compacted soil within such a short period of 3 months.
2) For a physically inadequate soil with the high mechanical impedance and low gas diffusion rate, the root of Pigeon pea could penetrate well as far as the soil was not highly acidic.
3) It was expected that the biopores in soil produced by the decomposition of roots would improve the drainage of soil.
4) Dry weight of the plant top of Pigeon pea was estimated as much as 10 t/ha, which carbon-nitrogen ratio was 24 or so, making it possible to utilize as a green manure.
