EFFECTS OF SOIL COMPACTION ON THE DEVELOPMENT OF RICE AND MAIZE ROOT SYSTEMS

The aim of this study was to determine the effects of soil compaction on the development of root system components of rice (Oryza sativa L.) and maize (Zea mays L.). Plants were grown for 4 weeks in root boxes (24 cm long x 2 cm wide x 40 cm deep) with soil bulk densities of 1.33 g/cm3 (control) and 1.50 g/cm3 (compact). In the compact treatment the main root axes of rice never penetrated beyond the 10-15 cm soil layer even by the fourth week, while seminal and seminal adventitious roots of maize had penetrated 30-35 cm deep by the third week. Generally, growth of higher order (second and third) lateral roots compensated for the restricted growth of the main root axes in both species. The ratio of first order L-type laterals producing higher order laterals on their axes was greater in the compact treatment for rice, while that of maize was not significantly increased. The root growth responses of rice and maize to soil compaction were different in the downward penetration of the main axis and the growth of the higher order laterals.