Influences of organic and synthetic soil fertility amendments on nematode trophic groups and community dynamics under tomatoes

Abstract

Research was conducted to examine the effects of organic and synthetic soil amendments and tillage on nematode communities in field soils planted to tomato ( Lycopersicon esculentum) at two locations. The experimental design was a replicated split plot with chisel-plow tillage and bare-soil or chisel-plow tillage and surface mulch with wheat straw as main plots, and soil amendments of synthetic fertilizer, composted cotton-gin trash, swine manure, or a rye-vetch green manure as subplots. Tillage did not affect free-living or plant-parasitic nematode community dynamics, but soil amendments had a large impact on nematode community structure and diversity. Populations of bacterivorous nematodes mainly in the Rhabditidae and Cephalobidae, and fungivorous nematodes were greater after planting in soils amended with swine manure, composted cotton-gin trash, or rye-vetch, than in soils amended with synthetic fertilizer at both locations. Populations of nematodes in these trophic groups decreased through time in each year. Populations of Meloidogyne incognita in soil were not affected by soil amendments, but increased through time at each location. Root-gall indices were lower in plots containing swine manure or cotton-gin trash than in those with synthetic fertilizer or rye-vetch during the second season. The combined nematode maturity index values were greater at planting in soils amended with rye-vetch or fertilizer than in soils with swine manure and composted cotton-gin trash. Shannon’s diversity index decreased over time for both years at one location, regardless of soil amendment. At the second location, the Shannon’s diversity index decreased only in the second year. Use of descriptive indices, including the Enrichment index, structure index, and channel index provided useful information about the effects of organic amendments on the structure of nematode communities in tomato field soils.