Influência dos sistemas de cultivo orgânico e convencional de algodão sobre a qualidade do solo no município de Tauá - CE.

Abstract

This work aimed at evaluating physical, chemical and biological soil properties/characteristics under cotton cultivation at Tauá-CE to test the hypothesis that organically managed cotton provides a better soil quality than conventionally managed cotton. We then selected six organically managed areas and three conventionally managed areas, with similar soils and topography. In each of the chosen areas, we set three sub-plots with the adopted multicrops, approximately 1 0 0 m2 each sub-plot, which served as replications in each area. Soil quality indicators analyzed were physical, chemical, and biological properties/characteristics. The experiment was developed in a randomized blocks design. Results were submitted to an analysis of variance, averages were then compared by Tukey’s test, on a 5% probability levei. Soi! physical aspects under conventional management showed a decrease in aggregates percentage and porosity when compared to organic management. When we compared the different areas, we observed that organic areas 1, 2 and 5 showed higher nutrient leveis than conventional areas (7, 8 , and 9) and the other organic areas (3, 4, and 6 ). Organic management system, from 1997 to 2000, improved chemical properties analyzed, especially where the system has been established for a longer time and where manure has been applied. Organic carbon, P and bases sum were increased and C/N ratio decreased. The conditions o f the soil environment under organic management favored soil macro and mesofauna, promoting a greater diversity under organic than under conventional management system. This survey has concluded that organically managed areas showed greater ability to improve soil quality as compared to conventional management, especially due to crop rotation, organic fertilizers application and less soil movement, allowing an increase in soil organic matter content.