Effects of different new types of fertilizer on yield, nitrogen use eiificiency and economic benefit of double cropping rice

objectives The application of new types of fertilizer has been regarded as one of the effective measures to improve fertilizer utilization efficiency and reduce soil degradation in China. However, it is unclear how to achieve high yield of the early and late season rice simultaneously by new types of fertilizer and fertilization methods.

Methods A successive two-year four-season double-cropping rice ‘Longxiangyou Huazan’, ‘Lingliangyou 7717’ were used as experimental materials to conduct field experiments on the basis of 189 kg/hm² nitrogen application. A two-factor split-plot design was adopted. The main plot was composed of no fertilizer (CK), compound fertilizer (CK1), stable compound fertilizer (T1), lignin slow-release fertilizer (T2, T3), rooting slow-release fertilizer (T4), organosilicon water-soluble slow-release fertilizer (T5) and controlled release fertilizer (T6) are six different fertilizer treatments. In the sub-region, there are five nitrogen application modes: 4∶2∶2∶2, 6.5∶3.5, 5.5∶4.5, 7∶3, 6∶4. The effects of new fertilizers on soil fortility (Nemero index method), rice yield, nitrogen application model and economic benefits were analyied.

Results The improvement of soil comprehensive fertility index by two-year rice was the largest in T3 (5.5∶4.5), followed by T2 (5.5∶4.5) and T5 (6.5∶3.5) . The results of Nemero index method for soil comprehensive fertility evaluation were basically consistent with the actual productivity of the soil. Higher soil fertility can characterize the high yield of crops. Yield analysis showed that the number of grains per panicle in early rice and seed-setting rate in late rice was significantly correlated with the corresponding rice yield. Therefore, the high-yield cultivation strategy of early and late rice should focus on the number of grains per panicle on the basis of maintaining the appropriate effective panicles and seed setting rate. In 2017 and 2018, the yield of all fertilization treatments was higher than that of CK without fertilization. Among them, the yield of T3 treatment was the highest, 16.69 and 16.67 t/hm², respectively. Compared with CK, the yield increased by 26.05% and 27.15%, respectively. At the same time, the integrated fertility index (IFI) of soil was promoted, and the IFI was 1.68 before fertilization. In 2018, compared with CK1, the yield of T3 treatment increased by 9.23%, the agronomic utilization rate of nitrogen fertilizer increased by 237.36% (P < 0.01), partial productivity of nitrogen fertilizer increased by 28.28% (P < 0.01) and the economic benefit increased by 51.6%.

Conclusions Lignin slow-release fertilizer (5.5∶4.5) application can promote double-cropping rice to obtain high yield and high economic benefit, that is, improve the soil comprehensive fertility, and increase the utilization rate of nitrogen fertilizer, which is a recommended fertilization method.