ROOT GROWTH OF UPLAND RICE GENOTYPES AS INFLUENCED BY NITROGEN FERTILIZATION

The plant root system is an important organ which supplies water and nutrients to growing plants. Information is limited on influence of nitrogen fertilization on upland rice root growth. A greenhouse experiment was conducted to evaluate influence of nitrogen (N) fertilization on growth of root system of 20 upland rice genotypes. The N rate used was 0 mg kg^?1(low) and 300 mg kg^?1(high) of soil. Nitrogen X genotype interactions for root length and root dry weight were highly significant (P < 0.01), indicating that differences among genotypes were not consistent at two N rates. Overall, greater root length, root dry weight and tops-roots ration were obtained at an N fertilization rate of 300 mg kg^?1compared with the 0 mg N kg^?1soil. However, genotypes differ significantly in root length, root dry weight and top-root ratio. Nitrogen fertilization produced fine roots and more root hairs compared with absence of N fertilizer treatment. Based on root dry weight efficiency index (RDWEI) for N use efficiency, 70% genotypes were classified as efficient, 15% were classified as moderately efficient and 15% were classified as inefficient. Root dry weight efficiency index trait can be incorporated in upland rice for improving water and nutrient efficiency in favor of higher yields.