Mitigação da compactação do solo em plantio direto.

Abstract

n Brazil, approximately 30 million hectares are managed under no-tillage. This practice has provided economic and environmental benefits for the country; however, the soil under no-till has shown a widespread problem: soil compaction. This physical degradation, identified in the subsurface layer (between 0.07 to 0.20 m), by confining the roots of the crops in the first centimeters of the soil profile has favored reduced yields of agricultural crops in the event of short-term droughts, harming the country economy. Thus, in order to generate knowledge relevant to the mitigation of soil physical degradation under no-till, which would allow reducing the risks of the crop failure due to short-term droughts, four independent studies were performed, in field experiment in the plateau region of the state Rio Grande do Sul, seeking answers to the following questions: i.) which is the persistence of the effects provided by scarifying the soil on its physical properties and crops root development in areas under no-till? ii) seeders equipped with deep action shanks (17 cm) can potentially alleviate soil physical degradation and promote deeper crop root growth of plants in the soil under no till? iii) which is the effect of mechanical management of soil compaction in the compacted layer soil aggregation? iv) which is the contribution of the vertical stratification of the chemical attributes on concentration the root system in the first cm of the soil profile? The results indicate that: soil chiseling has positive effects on soil physical properties and the development of plants, nevertheless, these are ephemeral, lasting less than two years; seeders equipped with deep action shanks has the potential to alleviate the physical degradation of the soil under no-till; after two years managing the soil with seeder equipped with deep action shank and soil chiseling, it was not observed any significant effect on the soil aggregation; and, the vertical stratification of soil chemical properties in the area under tillage has very small contribution to the limited root development of crops in the subsurface soil layer, with high soil resistance to mechanical penetration being the main factor to decrease the roots growth rate in this layer. Through these studies it can be realized how difficult it is to rehabilitate the structure of the Oxisols managed under no-till in the Brazilian subtropical region. This cannot be achieved by simply adopting mechanical methods.