Comunidade de nematoides como bioindicadores de qualidade do solo de um sistema de integração lavoura-pecuária

Abstract

The crop-livestock integration (ILC) when there is a good managed increases economic gains and improves the quality of the environment. However, the excess of the animal load in the pasture of the ILP can cause damages to the soil and decrease these benefits. Nematodes are bioindicators that can be used to evaluate the effects of increasing grazing intensity on soil quality. The objective of this work was to evaluate the soil quality of a crop-livestock integration system through the study of phytoparasite and free-living nematode communities. The experiment was conducted in an area of 22 hectares that at 15 years is cultivated with the succession Glycine max for grain production in summer and Avena strigosa + Lolium multiflorum for continuous grazing of cattle in winter. The treatments are composed of grazing plots at heights of 10, 20, 30 and 40 cm, plots without grazing and a natural pasture area. Soil samples were collected in soybean and pasture for quantification and identification of nematodes at the generic and trophic levels. The chemical, physical analyses, and soil cover properties were determined for correlation purposes. Due to degradation of the natural pasture, its conversion to agricultural area improved the status of the soil nematode community. The introduction of crop-livestock integration in the agricultural area also resulted in improvement of the soil nematode community. The increase in grazing intensity had different impacts in winter and summer, and the grass height of 20 cm resulted in better soil status community of soil nematodes. Eleven genera of parasitic nematodes of plants were identified, but all abundances were below the levels of economic damage. The grazing performed at 20 and 30 cm showed the lowest phytonethoid populations in summer and winter. The genus Helicotylenchus was dominant in all soil uses, but only the H. dihystera species is present. Meloidogyne javanica occurs in pasture areas with 40 cm and in natural pasture, in summer and winter. The conditions of this ILP limit the development of phytopathogenic nematodes, but if grazing is continued at 10 cm in winter, these nematodes could become a phytosanitary problem for soybeans grown in succession.