Abstract: Soil health is a key factor affecting the productivity of plant breeding bases. Soil nematode is an important bioindicator of soil health, with the community composition and diversity of which can reflect soil health conditions. To understand the soil ecological environment of different crops in the Plant Breeding Base of Sanya, soil samples from eight crops including rice, corn, sorghum, soybean, pumpkin, pepper, cotton, and watermelon were collected. The soil nematode community structure characteristics under different crops were analyzed by comparing nematode ecological indices. The results showed that the average individual density of nematodes was relatively low (43 individuals·100 g^-1 dry soil) in eight crops, and total 25 genera were identified. The largest number of nematodes and genera was found in pepper and the least one in watermelon. The Shannon diversity index of soil nematode was significantly different among different crops, with the highest index in soybean and the lowest one in watermelon. There were significant differences in the relative abundance of bacterivores and omnivores/predators among different crops. The relative abundance of bacterivores in watermelon and pepper was significantly higher (91.1% and 80.2%, respectively) than that in soybean and rice (47.4% and 31.7%). The relative abundance of omnivores/predators in rice was the highest (27.3%), which was significantly higher than that of the other seven crops. Tylenchorhynchus (plant parasitic nematode) was found in soils of all eight crops, while Hirschmanniella was only found in rice soil. The decomposition of soil organic matter in eight crops mainly depended on bacterial pathway. There were significant differences in free-living nematode maturity index (MI) among different crops, and the MI value of rice soil was the highest, which was significantly higher than that of other crops, indicating that the nematode community structure of rice soil was more complex and mature. There were no differences in nematode enrichment index (EI) and structure index (SI) among different crops. Rice soil had the highest SI, indicating that its soil environment was undisturbed and the food web was at a structured state. The soil environment of the other seven crops was stressed, with degraded food webs.

Key words: soil nematode, community structure, diversity index, maturity index, nematode faunal analysis