Abstract:

We evaluated the effects of 4 years of straw returning (2007-2011) on the nematode communities of the purple soil area in the hilly areas of central Sichuan basin, China, using the four treatments of 100, 50, 30, and 0% of straw returned to cropland. The Baermann method was used to extract nematodes from soil samples (0-15 cm). A total of 2,380 individuals, belonging to 2 classes, 8 orders, 24 families, and 39 genera, were extracted. The dominant genera included Tylencholaimus and Prionchulus, comprising 31% of total soil nematode individuals. Our results showed that soil nematode communities differed among the four treatments. Densities of the total nematode community, and fungivores and predators-omnivores specifically exhibited greater fluctuations with reducing straw return levels, while densities of bacterivores increased with reducing straw levels. Plant-parasite density, diversity index(H'), plant-parasite index (PPI) and Wasilewska index (WI) first increased and then decreased with reduction of straw return, while genera number, free-living nematode maturity index (MI) and channel ratio (CR) presented the opposite trend. Nematode diversity index (H') was highest at 30-50% straw return levels. But there were no significant differences among treatments for all of the indexes. The content of soil available potassium, which significantly increased at the lower levels of straw return, was significantly correlated with diversity indices of nematode communities. Our results suggested that straw return management changes the nematode community through its action on the content of soil available potassium, and that level of 30-50% of straw returning were optimal in the hilly areas of central Sichuan basin in terms of maximizing nematode diversity.

Key words: amounts of straw returning, soil nematode, diversity, community structure, trophic groups