ROOT DEPTH AND ROOTING DENSITY OF UPLAND RICE UNDER RAINFED CONDITION

Abstract

Upland rice, Kao Nong Hoi (local variety), was seeded on Typic Paleaquults, Fine loamy soil under rainfed condition at the experimental. farm, Faculty of Agriculture, Chiang Mai Unversity with row spacing of 30 cm and seed rate of 12 g/m. Root depth, no. of roots, and root density were measured by Frame Monolith method at 30 DAE (day after emergence.) and every 15 – day interval thereafter through out the growing period. Undisturbed soil samles were taken to dertermine soil bulk density by Core method and soil moisture content by Gravimetric method at the time of root sampling.

The results showed that upland rice roots penetrated to 60 cm. depth after 30 DAE. Root penetration was 70, 80 and > 100 cm deep after 45, 60 and 75 DAE, respectively. Number of roots and root density were maximum at 90 DAE on the top soil (0 – 10 cm.) and decreased rapidly with soil depth. This was probably associated with the increase in soil bulk density at the lower depth. Number of roots and root density were correlated with soil depths. These correlations were of exponential sigmoid nature at every stage of growth. The highest root density was found to be 3.2 cm/cm³ at 30 DAE on the top soil. Since moisture status at various soil depths was adequate, root growth patterns of the upland rice in the present study thus demonstrated its growth characteristics in accordance with different soil depth properties.