Among the various factors that contribute to high yields in agriculture, the good development of root system is considered one of the most important. In this research, the cause of soybeans root system growth variation was investigated. Soybeans sowing was made in two adjacent areas in the same type of the soil. In one of the areas, a no tillage system was used following Crotalaria juncea crop. In another area, the conventional management of soil was used. The variables analyzed showed that. 1) using the conventional management, the soil fertility starting from 10 cm layer to the depth of 120 cm showed adequate conditions for plant growth; 2) the concentrations of P, K and Ca of the aboveground parts of soybeans cultivated in the seven layers of the two soil profiles also confirm the better growth conditions under conventional management; 3) the area where C. juncea was planted and followed by soybeans in the no tillage management, showed hardness of the soil when compared with the conventional system. This result indicates a compactness of the soil at different layers; 4) in spite of the unfavourable conditions for the development of the root system, in the area where no tillage system was used, soybeans roots penetrated deeper than 1.2 m with nodules distributed along the profile. This was not observed in the conventional system of soil management. A probable explanation is that the vigorous taproot of C. juncea which penetrated the soil after its decomposition left the space to be filled up by the root system of the soybeans.
Crotalaria juncea L.; green manure; roots; soil management; soybeans