Conservation agriculture (CA) is defined by the simultaneous application of three basic principles: minimum soil disturbance, permanent organic soil cover and a diversity of species grown. These three principles are complemented with other practices such as the use of improved seeds; integrated crop nutrition; integrated management of pests, diseases and weeds; and efficient water management (Kassam et al., 2011). CA is indeed a structured integration of zero tillage with already existing practices from organic agriculture (mulching, rotations, legume cropping), biotechnology and breeding (improved seeds), integrated pest management and precision farming (for input application). No-tillage technology expanded from 45 million hectares in 1999 (Derpsch, 2001) to 117 million hectares in 2008/2009 (Derpsch and Friedrich, 2009b; Kassam et al., 2011) and 125 million hectares in 2011 (FAO 2011).

• Diversity. No tillage safeguards soil biodiversity and the functioning of biological processes above and below the soil surface, and rotations and manuring benefits agroecosystem biodiversity. CA systems are particularly adapted for agroforestry since crops and trees can be grown easily in close vicinity without the disturbance of tree roots inherent in tillage-based agriculture (Sims et al., 2009). However, many CA benefits, including those on biodiversity, depend on how weed control is managed, as weeds are the major challenge of no-till systems (Holland, 2004). Different results can be expected from IPM treatments, GMO and glyphosate combinations or manual weeding in low financial input systems with main products targeting non-cash crop, domestic markets.

• Coherence. CA’s use of no-till, rotations and mulching benefits farm soil organic matter and nutrient cycles, increases soil biomass and positively impacts soil moisture retention which, in turn, reduces irrigation requirements. Conservation agriculture, whether done by hand on small farms or mechanized on large farms, tends to reduce overall labour requirements and redistribute labour bottlenecks more evenly throughout the cropping cycle, particularly benefitting small-scale farmers with scarce labour availability.

• Connectedness. In general, no-till systems are associated with greatly reduced rates of soil erosion from wind and water (Schuller et al., 2007), higher rates of water infiltration (Wuest et al., 2006), groundwater recharge and enhanced conservation of soil organic matter (West and Post, 2002), with related benefits to watershed recharge and soil carbon sequestration, especially when implemented on large areas. In the USA, the adoption of no-till has increased soil organic carbon by about 450 kg C ha-1 yr-1, but the maximum rates of sequestration peak 5–10 years after adoption and slow markedly within two decades (West and Post, 2002). It is assumed that such a new equilibrium of soil organic matter with no further increase on cropland will be reached after 25–50 years (Reicosky and Saxton, 2007). In the tropics, soil carbon may increase at greater rates (Lovato et al., 2004; Landers et al., 2005).

• Efficiency. Crop yields and soil carbon per unit of inputs can be increased substantially with conservation agriculture. In general, the system production efficiency in CA is significantly increased as compared to conventional high external input farming systems thanks to increasing yield levels (up to 10 percent per year) and reduced requirements for water (-30 percent), energy (-50 percent), labour (-50 percent), fertilizer (-30 to ‑50 percent) and pesticides (-20 percent) (FAO, 2008; Saturnino and Landers, 2002; Lindwall and Sonntag 2010; Baig and Gamache, 2009).

• Resilience. CA improves resilience against extended drought and reduced water availability, and extreme weather events such as torrential rainfall, strong winds and extreme temperatures (hot and cold). In addition, rotations in the production systems make farmers less vulnerable in case one crop fails. The use of genetically modified seeds in CA systems, which increase the dependence on external inputs from limited suppliers and related fluctuations in terms of availability and price increases, can also increase the vulnerability of these systems to macro-economic risks.

Capacity for a green economy. Crop yields increase in conservation agriculture in the long-term. However, significant yield increases can also be achieved in the short‑term in low production systems on degraded soils. CA is an effective example of how increased productivity can be combined with decreased environmental impact, especially in areas endowed with large availability of natural (land and water) and economic (financial capital) resources, such as many areas in Latin America. However, it has to be recognized that much of the potential decrease of environmental impact is related to actual application of integrated weed control management (e.g., with low input of herbicides) and diversified rotations. In addition, permanent no-tillage may result in soil compaction, particularly with large-scale mechanized systems that will most likely have to revert to controlled traffic concepts (i.e. confining all agricultural machinery to the least possible area of permanent traffic lanes).