Conservation agriculture - A portuguese case study

This paper gives a glance about the conservation agriculture concept and the worldwide increase in agricultural area where this technique has been adopted. The main constraints to agricultural production in the Mediterranean region are discussed, highlighting the importance of conservation agriculture to mitigate them. Results of long-term studies with this technique, in Portugal, showed an increase in organic matter, improvement of aggregates stability and continuity of biological porosity along the soil profile. These changes in soil properties are helping to overcome edaphic and climatic constrains under Mediterranean conditions. The saturated hydraulic conductivity is improved allowing a better drainage during wet winters, and together with higher soil cohesion, the transitability of the soil is enhanced, allowing a correct timing of field operations like nitrogen top dressing and herbicide application. Nitrogen-use efficiency is improved either by the timing of application and by the improvement of soil organic matter content. Soil productivity is also enhanced and the overall energy-use efficiency is double when soil organic matter content is raised from 1 to 2% in the top 30cm of the soil. Therefore, conservation agriculture is advantageous from the economic and environmental point of view contributing to the sustainability of rainfed agriculture.