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Abstract
Human efforts to produce ever-greater amounts of food leave their mark on the environment. Persistent use of conventional farming practices based on extensive tillage, especially when combined with removal or in situ burning of crop residue, have magnified soil erosion losses and the soil resource base has been steadily degraded. Another direct consequence of farmers’ persistent use of traditional production practices is rapidly increasing production costs; the costs of inputs such as improved varieties and fertilizers continue to increase and farmers make inefficient use of them. Despite the availability of improved varieties with increased yield potential, the potential increase in production is not achieved because of poor crop management systems. Nowadays, people have come to understand that agriculture should not only be high yielding, but also sustainable. Conservation agriculture (CA) has been proposed as a widely adapted set of management principles that can assure more sustainable agricultural production. Conservation agriculture is a broader concept than conservation tillage, a system where at least 30% of the soil surface is covered with crop residues after seeding of the next crop. In CA, the emphasis not only lies on tillage components but on the combination of the following three principles: 1. Reduction in tillage: The objective is to achieve zero tillage (i.e., no tillage at all); however, the system may involve controlled tillage seeding systems that do not disturb more than 20–25% of the soil surface. 2. Retention of adequate levels of crop residues and soil surface cover: The objective is the retention of sufficient residue on the soil to: protect the soil from water and wind erosion; reduce water run-off and evaporation; improve water productivity; and enhance soil physical, chemical, and biological properties associated with long-term sustainable productivity. 3. Use of crop rotations: The objective is to employ diversified crop rotations to: help moderate/mitigate possible weed, disease and pest problems; utilize the beneficial effects of some crops on soil conditions and on the productivity of the next crop; and provide farmers with economically viable options that minimize risk. These CA principles are applicable to a wide range of crop production systems from low-yielding, dry, rain-fed conditions to high-yielding, irrigated conditions. However, applying the principles of CA will be very different in different situations. Specific and compatible management components such as pest and weed control tactics, nutrient management strategies, rotation crops, etc. will need to be identified through adaptive research with active farmer involvement. Conservation agriculture has been promoted as an agricultural practice that increases agricultural sustainability and is associated with the potential to lessen greenhouse gas emissions. There are, however, contrasting reports on the potential of CA practices for C sequestration (i.e., the process of removing carbon dioxide, CO2, from the atmosphere and depositing it in the soil).