Maize (Zea mays L.) is Mexico's primary staple food, but the Country's degrading soils and climate variability limit its productivity. Conservation agriculture (CA), a management technique that combines minimal tillage, permanent soil cover, and crop diversification, could reduce soil degradation and help improve soil health. There is however a lack of information about the effects of CA on soil health in the diverse agroecological conditions in Mexico. This study reports results of a field trial network established to adapt CA to Mexico's diverse cropping systems and local conditions.Physicochemical soil health, also referred to as soil quality, was studied in 20 trials in agro-ecologies ranging from handplanted traditional systems to intensive irrigated systems, initiated between 1991 and 2016. Soil in CA was compared to the local conventional practice (CP), which commonly involves tillage, residue removal, and continuous maize production. Across the sites, organic matter and nitrates were higher in the top (0-5 cm) layer of soil and soil aggregate stability was greater under CA than under CPs. For other soil health parameters, such as nutrient content, pH or penetration resistance, the effects of management varied widely across sites and soil types

Conservation agriculture, characterized by minimal tillage, permanent soil cover and crop diversification, has been widely adapted under rainfed conditions, but adoption under irrigated conditions is limited. An experiment initiated in 1997 to evaluate the level of tillage and the amount of soil cover needed for conservation agriculture to work under irrigated conditions in the highlands of San Luis Potosí, Mexico. The trial encompassed seven treatments: conventional tillage, two types of reduced tillage and permanent raised beds (PB), which are untilled, with four levels of soil cover in an irrigated rotation with maize (Zea mays L.) in the summer and fodder oats (Avena sativa L.) in the winter. Maize and oats yielded significantly more under PB than with tillage. Maize yielded on average 1.2 Mg ha−1 more in PB with the hybrid used from 1997 to 2008 and 3.9 Mg ha−1 more with the hybrid used from 2012 to 2017. Permanent raised beds generated on average $18,424 MXN ha−1 more profit than the tilled treatments and increased soil organic carbon on average 63% at 0 to 5 cm depth and 32% at 5 to 30 cm depth. The trial shows that conservation agriculture, with PB and little residue cover, is a viable and sustainable option in similar production systems.

In Mexico, conservation agriculture has been mainly implemented using permanent beds, where the top of the raised beds is not tilled, which allows them to obtain the benefits of conservation agriculture for yield and soil quality. However, narrow (0.75–0.80 m width) and wide (1.50–1.60 m width) beds are commonly implemented without scientific evidence available as to whether the width of the beds affects crop yields. The objective of our study was therefore to evaluate two types of permanent beds, in maize (Zea mays L.), wheat (Triticum aestivum L.), and barley (Hordeum vulgare L.) production, in various agro-ecological regions of Mexico. The study included nine sites, of which six were rainfed and three had irrigation. Bed width did not significantly affect crop yield. Therefore, farmers can choose the bed width that best meets their practical needs. Some practical considerations include mechanical weeding (more access in narrow beds), fuel use (lower for reshaping wide beds), irrigation water use (in wide beds similar to irrigating alternate furrows in narrow beds), and residue management (option to concentrate residue in windrows at center of wide beds). Soil texture can also affect this choice, because it affects water infiltration and retention.

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