Effects of nitrogen application regime on japonica rice yield and quality of the late rice in the double rice system in southern China

Objectives  “Indica to japonica” has been regarded as one of the effective measures to improve the rice yield and quality in the double-rice cropping systems in southern China. However, it is unclear how to achieve high yield and good quality of the late season indica-japonica hybrid rice simultaneously by nitrogen application regimes.

Methods  Field experiments were conducted in 2016–2017, the indica-japonica hybrid rice Yongyou 1538 was selected as the late season rice material. With the same total N application rate of 255 kg/hm², nitrogen was applied in three regimes of basal, tiller and panicle fertilizer as 6∶2∶2 (A), 4∶2∶4 (B) and 2∶2∶6 (C). For A and C, the panicle-fertilizer was once applied at the final third leaf stage, whereas for B, panicle fertilizer was twice evenly applied at the final forth leaf stage (B1) and second leaf stage (B2). The dry matter accumulation, yield and quality of japonica rice were investigated and analyzed at harvest stage.

Results  Compared with the B treatments, the yield of the A and C treatments were decreased by 1.9%–4.8% and 4.9%–16.8%, respectively, while the yield of the B1 and B2 treatments were increased by 1.2%–3.2% and 3.8%–12.5%, respectively. The total dry matter accumulation of the B, B1 and B2 treatments was significantly higher than that of the A and C treatments (P < 0.05), especially in the heading-mature stage. The main reasons for the strong dry matter production capacity was the high LAI of high effective leaf and effective leaf for the B₁ plots and the high SPAD of flag leaf for the B₂ plots during grain filling stage. With the decrease of the proportion of the base fertilizer, the qualities for industrial processing, tasting and cooking and nutrition were improved, but the appearance quality and RVA spectrum became worse. In addition, the qualities for industrial processing, tasting and cooking and nutrition under the same basal-tiller fertilization application ratio were shown as B₂ < B₁ < B, while the appearance quality and RVA spectrum characteristic value showed the opposite trend, with the nutrition quality was B₂ > B > B_1.

Conclusions  The ratio of basal fertilizer: tiller fertilizer: panicle fertilizer: granular fertilizer as 4∶2∶2∶2 had the highest yields for the late japonica rice, and both the high yield and high quality can be achieved simultaneously with the ratio of basal fertilizer: tiller fertilizer: panicle fertilize of 4∶2∶4, and the split of panicle fertilizer was better than once application under the experimental conditions.