Effect of N management on development of roots in soil in upland rice
1998
Kondo, M. | Aragones, D.V. | Agbisit, R. (International Rice Research Inst., P.O. Box 933, 1099 Manila (Philippines))
In the 1995 wet season, a field experiment was conducted at the IRRI upland farm to understand the morphological development of the rice root system under different N-supplying environments. UPLRi-5 was grown under the following conditions: no N applied, ordinary urea in three equal splits applied (36, 53 and 76 days after sowing), and polyolefin-coated urea (POC urea) and ordinary urea applied by surface incorporation and basal placement. Root mass increased until the flowering stage and declined rapidly to maturity in all N environments. The direction of root growth was most horizontal between panicle initiation and flowering stage. At the tillering stage, root length density at the 0-10 cm layer was highest with basal band application of urea, followed by POC urea. This indicates faster initial root growth at the surface with early N supply. At the flowering stage, basal band, especially deep band with urea, stimulated root growth in the subsoil. In urea split application, root growth was suppressed in the 0-50 cm layer, tillers were more of the secondary type. Basal N supply therefore stimulates growth of main tiller and early tillers were more of the secondary type. Basal N supply therefore stimulates growth of main tiller and early tillers which bear longer roots, resulting in a large rooting zone at the reproductive stage. Topdressing of N increased the number of late tillers with fewer and shorter roots which are mostly found in the shallow soil profile
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