Effects of Nitrogen Fertilization on Lodging Resistance of Directly Seeded Rice Plants in Crayfish-Rice

  Objective  Crayfish- rice mode is the important mode for agriculture production in Hubei and even southern China. Lodging is one of the main factors that affect the yield of rice. The study on the suitable nitrogen application rate of direct seeding shrimp rice can provide a theoretical basis for its rational fertilization.

  Method  Under the continuous cropping mode of crayfish-rice, using typical crayfish-rice varieties Yuzhenxiang, Huanghuazhan and Efengsimiao as experimental materials and no fertilization as control（CK）, a split plot experiment was set up at three nitrogen application levels (120, 150 and 180 kg · hm ^{− 2}) to explore the effect of nitrogen application rate on the lodging resistance of direct seeding crayfish-rice.

  Result  With increasing N application, the internode length, plant height, and gravity center height, bending momen of the 4^th and 5^th internode from the top, and big and small vascular bundles number of the 4^th internode from the top of the rice plants increased, while the breaking momente, big and small vascular bundles area, and culm wall thickness increased initially followed by a decline, and the lodging index decreased at first and then rose.

  Conclusion  The lodging resistance of the crayfish-rice cultivated rice plants in response to different N fertilizations varied among the 3 varieties. The optimal N application rate for Yuzhenxiang was 120 kg·hm⁻², for Efengsimiao 120-150 kg·hm⁻², and for Huanghuazhan 150 kg·hm⁻².