CONSERVATION AGRICULTURE
CA is based on optimizing yields and profits, to achieve a balance of agricultural, economic and environmental benefits. It advocates that the combined social and economic benefits gained from combining production and protecting the environment, including reduced input and labor costs, are greater than those from production alone. With CA, farming communities become providers of more healthy living environments for the wider community through reduced use of fossil fuels, pesticides, and other pollutants, and through conservation of environmental integrity and services.
Conservation agriculture is the integration of ecological management with modern, scientific, agricultural production. Conservation agriculture employs all modern technologies that enhance the quality and ecological integrity of the soil, but the application of these is tempered with traditional knowledge of soil husbandry gained from generations of successful farmers. This holistic embrace of knowledge, as well as the capacity of farmers to apply this knowledge and innovate and adjust to evolving conditions, ensures the sustainability of those who practice CA. A major strength of CA is the step-like implementation by farmers of complementary, synergetic soil husbandry practices that build to a robust, cheaper, more productive and environmentally friendly farming system. These systems are more sustainable than conventional agriculture because of the focus of producing with healthy soils.
Conservation agriculture promotes minimal disturbance of the soil by tillage (zero tillage), balanced application of chemical inputs (only as required for improved soil quality and healthy crop and animal production), and careful management of residues and wastes. This reduces land and water pollution and soil erosion, reduces long-term dependency on external inputs, enhances environmental management, improves water quality and water use efficiency, and reduces emissions of greenhouse gases through lessened use of fossil fuels. Conservation agriculture, including agroforestry (Figs. 1 and 2), specialty crops, and permanent cropping systems, promotes food sufficiency, poverty reduction, and value added production through improved crop and animal production, and production in relation to market opportunities. Reduced tillage leads to lessened human inputs, in both time and effort – this is generally attractive overall, but it is critical in HIV-affected regions.
Conservation agriculture is best achieved through community driven development processes whereby local communities and farmer associations identify and implement the best options for CA in their location. Local, regional and national farmer associations, working through community workshops, farmer-to-farmer training, etc., but with technical backstopping from conservation professionals, are the main players in the promotion of CA.
Conservation agriculture provides direct benefits to environmental issues of global importance. These include land degradation, air quality, climate change, biodiversity and water quality.
THE PRINCIPLES OF CONSERVATION AGRICULTURE
Conservation agriculture emphasizes that the soil is a living body, essential to sustain quality of life on the planet. In particular, it recognizes the importance of the upper 0-20 cm of soil as the most active zone, but also the zone most vulnerable to erosion and degradation. Most environmental functions and services that are essential to support terrestrial life on the planet are concentrated in the micro, meso, and macro fauna and flora which live and interact in this zone. It is also the zone where human activities of land management have the most immediate, and potentially the greatest impact. By protecting this critical zone, we ensure the health, vitality, and sustainability of life on this planet.
The principles of CA and the activities to be supported are described as follows:
• Maintaining permanent soil cover and promoting minimal mechanical disturbance of soil through zero tillage systems, to ensure sufficient living and/or residual biomass to enhance soil and water conservation and control soil erosion. In turn, this improves soil aggregation, soil biological activity and soil biodiversity, water quality, and increases soil carbon sequestration. Also, it enhances water infiltration, improves soil water use efficiency, and provides increased insurance against drought. Permanent soil cover is maintained during crop growth phases as well as during fallow periods, using cover crops and maintaining residues on the surface;
• Promoting a healthy, living soil through crop rotations, cover crops, and the use of integrated pest management technologies. These practices reduce requirements for pesticides and herbicides, control off-site pollution, and enhance biodiversity. The objective is to complement natural soil biodiversity and to create a healthy soil microenvironment that is naturally aerated, better able to receive, hold and supply plant available water, provides enhanced nutrient cycling, and better able to decompose and mitigate pollutants. Crop rotations and associations can be in the form of crop sequences, relay cropping, and mixed crops;
Promoting application of fertilizers, pesticides, herbicides, and fungicides in balance with crop requirements. Feed the soil rather than fertilize the crop. This will reduce chemical pollution, improve water quality, and maintain the natural ecological integrity of the soil, while optimizing crop productivity and economic returns;
• Promoting precision placement of inputs to reduce costs, optimize efficiency of operations, and prevent environmental damage. Treat problems at the field location where they occur, rather than blanket treatment of the field, as with conventional systems. Benefits are increased economic and field operation efficiencies, improved environmental protection, and reduced (optimized) input costs. Precision is exercised at many levels: seed, fertilizer and spray placement; permanent wheel placement to stop random compaction; individual weed killing with spot-spraying rather than field spraying, etc. Global positioning systems are sometimes used to enhance precision, but farmer sensibility in problem diagnosis and precise placement of treatments is the principal basis. In small-scale farming systems and horticultural systems, it also includes differential plantings on hills and ridges to optimize soil moisture and sunshine conditions;
• Promoting legume fallows (including herbaceous and tree fallows where suitable), composting and the use of manures and other organic soil amendments. This improves soil structure and biodiversity, and reduces the need for inorganic fertilizers;
• Promoting agroforestry for fiber, fruit and medicinal purposes. Agroforestry (trees on farms) provides many opportunities for value added production, particularly in tropical regions, but these technologies are also used as living contour hedges for erosion control, to conserve and enhance biodiversity, and to promote soil carbon sequestration.
Zero tillage is a 'cornerstone' of CA, and can be practiced in both large and small farming systems. With zero till (also termed no-tillage and direct drilling) the only tillage operations are low-disturbance seeding techniques for application of seeds and fertilizers directly into the stubble of the previous crop. Gradually, organic matter of the surface layers of zero tilled land increases, due to reduced erosion, increased yields resulting in more crop residue added to the soil surface, and differences in the assimilation and decomposition of soil organic matter. Gradually, an organic mulch is developed on the soil surface, and this is eventually converted to stable soil organic matter because of reduced biological oxidation compared to conventionally tilled soils. Zero tillage is effective in mitigating many of the negative on-farm and off-site effects of tillage principally erosion, organic matter loss, reduced biodiversity and reduced runoff. These conditions are replaced with permanent soil cover, improvements in soil structure, improved organic matter status, improved water use efficiency, and improved soil biology and nutrient cycling.
