Abstract: To explore the optimal nitrogen reduction ratio in the rice-crayfish co-culture system, a field experiment was conducted using conventional indica rice Ezhong 6 and hybrid indica rice Longliangyou 534 as test varieties, and five nitrogen application treatments were set up, including conventional nitrogen application rate (N4, pure nitrogen 180.0 kg/hm²), 10% nitrogen reduction (N3, pure nitrogen 162.0 kg/hm²), 20% nitrogen reduction (N2, pure nitrogen 144.0 kg/hm²), 30% nitrogen reduction (N1, pure nitrogen 126.0 kg/hm²), and no nitrogen application (N0). The differences of rice quality between the rice-crayfish co-culture system and the rice monoculture system were investigated, and the changes of protein, amylose and their key enzyme activities were analyzed. The results showed that under the rice-crayfish co-culture system, as the nitrogen fertilizer reduction ratio increased, the brown rice rate, milled rice rate, head rice rate, chalky grain rate, chalkiness and the total protein content of both varieties decreased, while the amylose content, gel consistency and taste value increased. No significant differences in processing quality or protein content were observed between the N3 and N4 treatments, whereas the N3 treatment demonstrated superior appearance, cooking, and eating quality. Compared with the rice monoculture system, the rice-crayfish co-culture system generally produced higher-quality rice. It could be seen that the synergistic goal of “nitrogen reduction-quality improvement-efficiency” could be achieved when the proportion of nitrogen fertilizer reduction was 10% under the rice-crayfish co-culture system.

Key words: rice (Oryza sativa L.), rice-crayfish co-culture, nitrogen reduction, rice quality