Structure of nodal root system of rice as affected by soil water regime and nitrogen
1998
Kondo, M. | Winn, Tu | Okada, K. (International Rice Research Inst., P.O. Box 933, 1099 Manila (Philippines))
In upland rice, a deep rooting system is important to ensure water uptake from the deep soil layer. The formation of the rooting zone is primarily governed by the expansion of nodal roots in rice. The effect of soil water and N on the length and elongating angle of the nodal root was analyzed with particular emphasis on the tiller-nodal root connection. Improved upland variety UPLRi-5, a traditional upland variety Moroberekan, Kinandang Patong (KP), and improved variety IR20 were grown in root boxes for 40 days under different N levels and water regimes (35 percent, 50 percent volumetric water content, and submerged soil). Roots of KP and Moroberekan were longest and had the deepest angle while those of IR20 were shortest and had the shallowest angle across all water regimes and N levels. IR20 had the largest number of roots because it had the highest tiller number and highest root number per tiller among the varieties. The number of nodal roots per tiller and the number of nodal roots per node were increased as the intensity of water stress was reduced, such that the total number of roots was highest in the submerged soil. Root length was reduced by N in submerged soil to a larger extent than by N in aerobic soil. It was found that the roots from the main tiller were deepest, followed by roots from the first order tiller. Roots from the lower nodes were longer and had deeper angle than those from the upper nodes, although this difference was less clear in IR20. The results imply that in upland condition, the roots which form the deepest portion of the rooting zone are mainly the roots from the lower node of the main tiller
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