Sustaining Global Food Security in A Changing Climate: Conservation Agriculture, Tillage Practices and Residue Management for Climate Change Adaptation and Mitigation Tested in Two Agro-Ecological Environments in Mexico.

In the sub-tropical highlands of Mexico, conservation agriculture (zero tillage with at least partial residue retention and crop rotation) has the potential to mitigate and adapt to climate change. Conservation agriculture results in high physical, chemical and biological soil quality that favours larger yields and reduces the net global warming potential compared to the traditional agricultural system (tillage, residue removal and monoculture of maize). The high physical soil quality ensures that the cropping system is optimized to cope with both heavy rainfall events and prolonged drought, events that are likely to increase in frequency due to climate change. Residue retention under zero and conventional tillage induces greater microbial diversity, especially higher total bacteria, fluorescent Pseudomonas and actinomycetes both for maize and wheat cropping systems. This diversity allows an ecosystem to remain stable when facing changes in environmental conditions. Although root rot is higher in zero tillage with residue retention than in the traditional agricultural system, it does not affect yields. The net global warming potential is near neutral in conservation agriculture, whereas systems involving conventional tillage or zero tillage contribute to global warming. Conservation agriculture requires the retention of at least part of the crop residue in the field.

In the irrigated arid north-western part of Mexico, the practice of permanent beds, where all or part of the residue is retained in the field, seems to be a more sustainable option for this irrigated wheat-based cropping system than conventional tillage with incorporation of the residues. Timely planting of wheat might help to prevent negative effects of global warming. Optimizing application fertilizer rates and synchronizing them with crop development will further increase yields while reducing costs and emissions of N₂O. More research is needed to determine net global warming potential of different practices and to further develop conservation agriculture systems and irrigation strategies with reduced irrigation requirements.

Complex, multi-component technologies, such as conservation agriculture, can be successfully scaled out through an innovation systems approach, implementing research and extension hubs that include functioning networks of farmer groups, machinery developers, extension workers, local business and researchers in order to develop and adapt technologies to local conditions. The case studies described in this chapter highlight the importance of key investments to establish several of those innovation systems in contrasting cropping systems in different agro-ecological environments in Mexico and world-wide.