Variation in nitrogen uptake efficiency in upland rice landraces as influenced by P fertilization

Abstract

Upland rice are usually planted on infertile soils that have been eroded and degraded. The high fertilizer inputs to poor nitrogen (N) content soils can increase plant production but are neither economically viable nor sustainable. Hence, this study was focused on P fertilizers effects on N use efficiency (NUE) of five upland rice landraces which was conducted at Carey Island, Selangor. The study was evaluated using two phosphorus levels (0 and 100 kg P/ha). A factorial experiment was conducted with four replications in randomized complete block design (RCBD). Ammonium sulphate fertilizer [(15NH4)2SO4] with 1% N-15 atom excess was applied as N-labelled fertilizer at the rate of 150 kg N/ha. The source of K in the form of muriate of potash was applied also at the same rate. Destructive sampling was carried out at week 4, 8 and 16 after transplanting and the NUE of the landraces were evaluated using isotope dilution technique. The P fertilization had no significant effect on NUE as well as on dry matter yield. These results suggested that P is not one of the limiting factors in plant growth and production as well as nitrogen use efficiency of these selected upland rice landraces. The dry matter yield and NUE were not significantly different among landraces at week 4 as the plants undergo their vegetative growth. These upland rice landraces showed significant differences in dry matter yield and nitrogen use efficiency at maturity stage (16 weeks). Landrace I showed significantly lower NUE compared to other landraces at week 16, while landrace III is the most efficient in utilizing nitrogen for production of dry matter.