[Effects of organic manure partial substitution for chemical fertilizer on the photosynthetic rate, nitrogen use efficiency and yield of rice].

Rational application of organic fertilizers is an effective approach to improve soil fertility, crop yield, and zero growth of chemical fertilizer in agricultural production. The rice variety 'Shennong9816' was planted in Shenyang, Liaoning Province, under seven different treatments: zero nitrogen fertilizer (CK), low nitrogen, 150 kg·hm ^-2 (LN), medium nitrogen, 240 kg·hm ^-2 (MN), high nitrogen, 330 kg·hm ^-2 (HN), medium nitrogen with replacement of chemical N by 10% organic manure (OMN ₁₀ ), medium nitrogen with replacement of chemical N by 20% organic manure (OMN ₂₀ ), and medium nitrogen with replacement of chemical N by 30% organic manure (OMN ₃₀ ). The effects of different treatments on photosynthetic rate, nitrogen absorption, nitrogen use efficiency, and yield were examined and the optimal fertilization scheme was determined. The results showed that the photosynthetic rate, biomass and yield were increased with the increases of nitrogen application rate, while the nitrogen use efficiency was decreased significantly. Compared with the MN treatment, the photosynthetic rate of OMN ₁₀ and OMN ₂₀ in filling stage was increased by 22.9% and 9.9%, respectively. The yield of OMN ₂₀ was increased by 3.8% compared to that of MN. The nitrogen agronomic efficiency and physiological efficiency of OMN ₂₀ were significantly improved by 8.1% and 13.3%, respectively. Moreover, the nitrogen agronomic efficiency and physiological efficiency of OMN ₂₀ were improved by 27.2% and 37.2% compared with the HN treatment. Thus, we concluded that the organic fertilizer replacement treatment could conserve soil fertility, achieve high yield and high nitrogen use efficiency, while reduce chemical nitrogen fertilizer application. The OMN ₂₀ treatment was recommended as a fertilizer application model due to its superior performance among the seven treatments.