Social and income trade-offs of conservation agriculture practices on crop residue use in Mexico's central highlands

Conservation agriculture (CA) is promoted worldwide to enhance soil quality, improve farmers' incomes and increase the resilience of rainfed agro-ecosystems under climate change. A major constraint to the adoption of CA is crop residue management in mixed crop-livestock systems. Farmers have competing uses of crop residues - for soil cover, as fodder or as additional income source - which may explain low CA adoption rates in some countries. This paper describes the social and income trade-offs of different crop residue uses in Mexico at regional, community and household level associated with the introduction of CA. We first spatially analyze the importance of crop residues for fodder supply and identify municipalities with fodder surplus at national and regional level. Second, we assess the likely social trade-offs and implications for farming communities of changing a typical farm households' residue allocation. Third, we identify the effects of crop residue uses on gross margins of maize and barley and assess the economic optimal crop residue allocation at the farm level with short planning horizons. The paper focuses on maize and barley producers in the central Mexican highlands and combines primary quantitative and qualitative data with secondary data. Analysis shows that at a national level, Mexico has a fodder surplus while the central highlands have a deficit. Crop residues are a major fodder source in Mexico, contributing up to 40% of fodder availability. Crop residues are also an important income source which implies costs for introducing CA in the central highlands. Our analysis indicates that retaining crop residues in-situ influences gross margins and that retention of roughly 45% of residues maximizes gross margins in situations where opportunity costs for the use of crop residues exist. Partial residue retention, sequential introduction and combination of technologies may facilitate CA uptake but CA remains a challenge for resource-poor farmers given their limited liquidity, risky production environment and difficulty to forego current income for future benefits. More interdisciplinary research is needed around economic optimal residue retention levels under different farming and production conditions, to identify the ecological needed minimum cover of crop residues for CA and to develop alternative low-cost sustainable technologies with short-term benefits. (C) 2014 Elsevier Ltd. All rights reserved.