Conservation Agriculture to Rebuilt Soil Fertility in Northern Tunisia

Tunisia is an agriculture country. Such as many other Mediterranean countries precipitations  remains a decisive factor not only for the different agricultural uses of lands (rainfed or irrigated system) but also for the soils erosion. The latter  is accentuated by agricultural practices (tillage, pesticide inputs, low crop residue restitution…) which are often productive but do not protect natural resources. All these factors have led to the development of conservation agriculture based on no-tillage as a mean to combat soil erosion. In fact, in Tunisia, no-tillage areas increased from 52 ha in 1999 to 17000 ha in 2020. Based a set of 20 plots covering 6 soils types and located in the semi-arid area of the country, a periodic monotoing of a set of soil parameters were done during three years, which include soil sensitivity to erosion according Le Bissonnais method, soil organic matter content and soil microbial respiration. For each plot, a half  of the surface was no-tilled and the other half was conducted according the conventional method based on soil returning. The results show a rapid effect of no-tillage on soil erosion, since an improvement of 18%, 42% and 39% of soil resistance to erosion, respectively after the first, second and third year of switching to no-tillage system. The soil microbial activity response was also significative, whit a progressive increase of soil respiration in the no-tilled treatments compared to tilled treatments. The microbial respiration was higher in non-hydromorphic soils and particularity in the red Mediterranean soils, calcic-magnesic soils and isohumic soils were moisture conditions was the most favorable for a development of soil microorganisms. For soil organic matter content, the evolution trend was not detectable in relation to the slow evolution of this soil parameter. However, the evolution of particulate organic matter content (a part visible of soil organic matter, with a size larger than 2mm) shown an increase in no-tilled treatments comparative to the tilled treatments. The increase of the particulate organic matter content was more important in vertisols, podzol, calcic-magnesic soils and isohumic soils in relation with their higher wheat production compared to other studier soil types.