[Effects of reduction of nitrogen fertilizer application and combined organic fertilizer on soil nematode community in winter wheat field]

Abstract

Soil nematodes are one of the typical indicator organisms for soil health. To reveal the effects of reduction in nitrogen fertilizer application on soil health, we examined community structure of soil nematode under reduced nitrogen fertilizer while combined with organic fertilizer at the jointing stage of winter wheat. There were six fertilization treatments, including CF(315 kg N·hm^-2, conventional fertilization), N₂₄₀ (240 kg N·hm^-2), N₂₁₀ (210 kg N·hm^-2)、N₁₈₀ (180 kg N·hm^-2), F₁₅₀ (180 kg N·hm^-2+150 kg·hm^-2 fulvic acid), and F₂₂₅(180 kg N·hm^-2+225 kg·hm^-2 fulvic acid). The results showed that: 1) The reduction of nitrogen fertilization decreased nematode number by 15.3%-68.5%. 2) Protorhabditis was the dominant genus (19.6%-50.4%) across all treatments. The reduction of nitrogen fertilizer application increased the abundance of fungivores, herbivores, and predators-omnivores, while that of bacterivores decreased first and then increased. Combined application of organic fertilizer decreased the abundance of bacterivores and fungivores, while increased that of herbivores and predators-omnivores. 3) N₂₄₀ and F₂₂₅ increased the Shannon diversity (H) of nematode community by 48.1% and 58.5%, respectively. The maturity index (MI) in N₂₄₀ was the highest (1.95), while the structural index (SI) was the lowest in N₁₈₀ (43.33). The structural index (SI) of F₂₂₅ with combined application of organic fertilizer reached 62.72, but its enrichment index (EI) was lowest (80.82). In conclusion, reduced nitrogen fertilizer application and combined with organic fertilizer could improve soil nematode diversity, increase the complexity of soil food web, which would be conducive to the health and stability of agricultural ecosystem.

Keywords: fertilizer application reduction; grey desert soil; soil health; soil nematode.