Evaluation of fertilizing schemes for direct-seeding rice fields in Taihu Lake Basin, China
Lin Zhang YANG
Field experiments were performed to identify an effective fertilizing scheme for direct-seeding rice (DSR) fields in the Taihu Lake Basin in east China. Based on local traditions, 3 typical fertilizing schemes (FS-1, FS-2, and FS-3) were evaluated, in consideration of ensuring a certain rice yield and relatively low nitrogen (N) loss. The base, seedling, tillering, jointing, and panicle fertilizers for FS-1 were all 20% of 270 kg N ha-1, those for FS-2 were 30%, 30%, 0%, 25%, and 15% of 270 kg N ha-1, and 15%, 20%, 25%, 20%, and 20% of 220 kg N ha-1 for FS-3, respectively. The results show that the majority of fertilizer N for DSR should be applied as topdressing fertilizer and not as base fertilizer as in transplanted rice cultivation. Increasing base fertilizer would not significantly improve the growth or yield of rice due to the low uptake of N during the seedling stage, and in turn would lead to greater N loss. Under FS-1, FS-2, and FS-3, N loss was 91.4, 103.1, and 70.5 kg ha-1, respectively, via surface runoff, volatilization, and leaching. Furthermore, using different fertilizer N methods during the rice growing season led to different N uptake by rice plants. In the present study N uptake by rice was measured at 108, 91, and 102 kg N ha-1 under FS-1, FS-2, and FS-3, respectively. At the same time, the rice yield with FS-1, FS-2, and FS-3 was 8530, 7780, and 8620 kg ha-1, respectively. In modern agricultural management an effective fertilizer scheme should simultaneously benefit both rice yield and the water environment. As a result, FS-3 was used in this study for DSR cultivation in the Taihu Lake Basin, which resulted in good rice yield and totally reducing N loss of 20.9-32.6 kg N ha-1.