Effects of Cultivation Mode and Nitrogen Application Rate on the Structure and Stability of Animal Community in Cotton Field

【Objective】 Different cultivation patterns and fertilization levels may affect the growth of cotton and then affect the occurrence of field pests. In this study, early maturing conventional cotton 50 was taken as material to study the effects of different cultivation patterns and nitrogen application on the community structure and stability ofarthropod communities in cotton field i n Dafeng, a coastal cotton area in the lower reaches of the Yangtze River, and Nanjing, a cotton area along the Yangtze River. 【Method】 The investigation experiment was started at the 3-leaf stage of the cotton in direct seeding cotton fields, and the investigation was started on the 3rd day after cotton transplanting in transplant cotton fields. A random survey was used to look at all organs of the cotton plant and record the species and numbers of all arthropods on the cotton plants. 【Result】 Compared with the amount of nitrogen application, the effects of different cultivation measures on the number of individuals and the ratio of natural enemies and pests in cotton fields were significant, and the trends were consistent. Compared with the direct seeding cotton field, the transplanting cotton field was more conducive to the occurrence of natural enemies, and the ratio of natural enemies and pests was higher. Different nitrogen fertilizer application date had no significant effect on cotton field insects. The results of relative abundance showed that aphis gossypii, cotton whitefly, cotton plant-bug and thrips were the main pests in the cotton fields, and chrysopids, spider and ladybird were the main natural enemies. The population dynamics of main pests showed that cotton aphid, cotton spider mite, cotton thrip, cotton whitefly and cotton plant-bug were concentrated in mid and late August and early and mid-September. There were more cotton aphid and cotton spider mite in direct seeding cotton field. The numbers of cotton thrip and cotton plant-bug were more in the transplanted cotton field. The number of cotton thrip was relatively large in the cotton field without nitrogen fertilizer. The number of whitefly was relatively large in the entire c otton field. The population dynamics of natural enemies showed that the number of chrysopid was more in late August and early and mid-September. Spider and ladybird were abundant in late June and early and mid-July. Spider and ladybird were more in the transplanted cotton field. The number of chrysopid and ladybird were more in cotton field with nitrogen fertilizer. The analysis of community parameters showed that the diversity index and uniformity index of pest sub-communities in transplanted-N₀ cotton fields were significantly higher than those in direct seeding-N₀ cotton fields in Nanjing, while the dominant concentration index was the opposite; The diversity index and uniformity index of natural enemy sub-communities in transplanted-N₁₀ cotton fields were significantly higher than those indirect seeding-N₀ cotton fields in Dafeng, while the dominant concentration index was the opposite. 【Conclusion】 The dynamics and occurrence of insects in cotton fields are slightly different due to different cultivation measures and nitrogen application. The pest sub-community has the highest stability in the transplanted-N₀ cotton fields, while the natural enemy sub-community has the highest stability in the transplanted-N₁₀ cotton fields. In general, there is no significant difference in the stability of arthropod community among the treatments.