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Intensive agriculture with deep tillage and soil inversion causes rapid soil deterioration with loss of soil organic matter content. This practice leads to a decrease of soil biological activity, a damage of the physical properties and a reduction of crop yields. Conservation agriculture aims to achieve sustainable and profitable agriculture through the application of three basic principles: minimal soil disturbance by conservation tillage, permanent soil cover and crop rotations. Any practice of conservation agriculture must maintain on the soil enough surface residues throughout the year. Conservation tillage is thus any tillage and planting system that maintains at least 30% of the soil surface covered by residues after planting to reduce soil erosion by water. Here we review the main advances about the adoption of conservation agriculture under Mediterranean conditions in Spain. There are major cost savings, e.g. fuel and fertilizer costs, compared with conventional agriculture. Conservation tillage has been proven to be highly efficient for water storage, to increase moderately the organic matter in the soil top layer, and to improve soil physical properties and aggregation. However, no tillage may induce greater soil compaction in some cases. In this case, an occasional tillage is advised. Furthermore, conservation tillage can reduce soil CO2 emissions, mobility and persistence of herbicides. In general, conservation tillage enhances biodiversity compared to conventional tillage. Crop yields under conservation tillage are similar or even greater than yields of traditional tillage. All these benefits show that -conservation agriculture in Spain is a more sustainable alternative than conventional agriculture. Nonetheless, we have found from the literature analysis some constraints for its adoption, mainly due to inadequate extension and technology transfer systems and lack of access to specific inputs. [ABSTRACT FROM AUTHOR]

A NSC for the transformation to the state affine systems of MISO nonlinear systems has been obtained. The main result is stated in terms of the I/O differential equation and some one-forms obtained in a straightforward way and easy to check. With the help of a regular transformation, one avoids the time varying computation of the observer gain matrice an then a Kalmanlike observer Σo (4.3) for the transformed system Σa (4.2) can be directly applied. [ABSTRACT FROM AUTHOR]