Environmental Effects of Soil Tillage.

Nowadays to soil tillage it has not only requested to improve crop yield, but also to contribute to mitigate environmental pollution. As regards the main effects of tillage on soil quality, the effects on soil organic matter (SOM) conservation, erosion control and soil compacting are presented. The impact of soil tillage on air quality is mainly related to its effect on oxidative activity into the soil. Tillage techniques that enhance oxidation could increase SOM degradation, thus increasing CO2 emissions. On the contrary, when tillage reduces soil porosity, it could increase anaerobic conditions, thus and ammonia emissions are also presented. Soil tillage effects on water quality are mainly related to the increases of oxidation and nitrification that lead to nitrate accumulation into the soil in a period characterized by leaching rainfalls and by low crop uptake (i.e. autumn in Mediterranean regions). Nevertheless it is not correct to generalize about the effects of soil tillage on environmental quality because they depend on complex interactions among tillage technique and the other components of the cropping system (weather, soil features, crop sequence, ...). Therefore a systemic approach is necessary to understand all the effects of soil tillage in the different agro-climatic conditions.