Effect of reduced phosphorus fertilizer on early/late season rice yield in South China

The main task of this study was to isolate suitable rice cultivars for early and late season cultivation in South China under reduced phosphorus fertilizer application and prove structural characteristics of rice yield. Four rice cultivars including two conventional fine grain quality rice cultivars (Vy: Yuejingsimiao No. 2; Vg: Guixiangzhan), a hybrid rice (Vh: Huayou 8305) and a super hybrid rice (Vt: Tianyou 998) were field-cultivated under 3 different super-phosphate application treatments (P0: 0, P1: 315.0 kg·hm^-2 and P2: 450.0 kg·hm^-2, respectively). Then population LAI, SPAD of flag leaf and leaf senescence index, yield and yield components of the rice cultivars were analyzed. The results show a significant super high yield in Vh as it has the highest per panicle grains under P0; and a significant high yield in Vt as it has a higher number of panicles, seed-setting rate and per panicle grains under P1. There is an insignificant effect of different levels of phosphorus application on Vg yield. Vy shows co-enhancement of effective panicle number and per panicle grains, obtaining significant high yields under P2. Therefore, among the rice cultivars for both the early and late season cultivation in South China, the conventional rice Vg, and the hybrid rice Vh are most suitable for reduced applications of both nitrogen and phosphorus fertilizers. Analysis of rice LAI, SPAD and leaf senescence index after heading suggests that the suitable population LAI along with a consistently higher SPAD of flag leaves and higher leaf senescence index forms the strong functional “source” at the later growth stage for the high yield of rice population.