Authors: Priyanka Singh and Mir Miraj Alli
Conservation agriculture (CA) can be defined by a statement given by the Food and Agricultural Organization of the United Nations as “a concept for resource-saving agricultural crop production that strives to achieve acceptable profits together with high and sustained production levels while concurrently conserving the environment” (FAO 2007).
CA is a set of soil management practices that minimize the disruption of the soil's structure, composition, improve soil fertility, reduce soil compaction and enhance soil exchange capacity, water infiltration and water holding capacity, soil biodiversity, resilience to climate change etc. Despite high variability in the types of crops grown and specific management regimes, all forms of conservation agriculture share three core principles. These include:
- Maintenance of permanent or semi-permanent soil cover (using either a previous crop residue or specifically growing a cover crop for this purpose).
- Minimum soil disturbance through tillage (just enough to get the seed into the ground).
- Regular crop rotations to help combat the various biotic constraints. When these CA practices are used by farmers one of the major environmental benefits is reduction in fossil fuel use and greenhouse gas (GHG) emissions. Even it also reduces the power/energy needs of farmers who use manual or animal powered systems.
Elements of Nutrient Management Strategy in CA
Being a biologically-based practice with an agro-ecological perspective, CA does not focus on a single commodity or species, instead it addresses the complex interactions of several crops. Nutrient management strategies in CA systems would need to attend to the following four general aspects, namely that:
- Managing Soil Biological Processes – Soil as a Living System The biological processes of the soil are enhanced and protected so that all the soil biota, microorganisms are privileged and that soil organic matter and soil porosity are built up and maintained. It can be managed by maximizing crop residue, applying compost or manure, growing cover crops, crop rotation, protect the habitat of soil organisms. Reduced tillage, lack of compaction, constant ground cover, and minimum disruption by chemicals protect the environment of soil organisms.
- Managing Biomass Production and Biological Nitrogen Fixation CA systems require higher levels of biomass production within the rotation to develop and maintain an adequate mulch cover, to raise soil organic matter level, to enhance soil biodiversity and their functions, to raise moisture and nutrient holding capacities, to enhance nutrient supplies, to enrich the soil with nitrogen in the case of legumes, and to protect the soil surface. Practices that enhance soil organic matter are built into CA principles and include one or more of the following: minimal or no-till, diversifying cropping systems, planting trees, mulching, using cover crops and green manures, using crop rotations, and using nitrogen fixing crops.
- Managing Access to a Balanced Nutrient Supply The more common notion regarding crop nutrition is based on maintaining overall quantities or concentrations of nutrients in the soil. At the practical level, this is reduced to a simple output input nutrient balance equation so that what is taken out by the crop is or must be replaced by application of nutrients from inorganic fertilizer or other sources. Invariably, this approach is combined with intensive soil tillage that reduces, over time, soil organic matter and porosity, and therefore also its water and nutrient holding capacity as well as all the beneficial soil biological processes.
- Managing Soil Acidity Soil pH is critical for several reasons. It has a major influence on the availability of elements, including primary nutrients like nitrogen, phosphorus and potassium, as well as secondary nutrients, micronutrients and potentially toxic elements like aluminum. Most soil microorganisms are sensitive to soil acidity, which has an influence on nutrient availability (especially nitrogen), soil organic matter and general soil health. The most beneficial soil fungi, for instance, do not like a high pH, and soil bacteria have problems at lower pH. One of the main reasons for managing soil pH by application of lime is to reduce such toxic effects. However, soil acidity becomes self-adjusting at 6.2 or 6.3 when all four cations -- calcium, magnesium, potassium and sodium -- are in proper equilibrium (Kinsey and Walters 2006). Any one of them in excess can push pH up, and any one of them in lower amounts can take pH down.
Conclusion
Many of the CA related soil processes, e.g. increased soil organic matter content and soil porosity, or increased biological nitrogen fixation by legumes in rotation, or exploitation of the deeper soil layers through crops with deep and dense root systems, have a significant bearing on nutrient management. Evidence shows that in CA systems, nutrient requirements are lower, nutrient efficiencies are higher and risks of polluting water systems with mineral nutrients lower. In CA systems, the focus is on managing soil health and productive capacity simultaneously and which depends on many complex cropping system relationships in space and time and on biodiversity and organic matter within soil systems when they are enlisted on behalf of agricultural production.
References
1. Food and Agriculture Organization (FAO). 2007. Agriculture and Consumer Protection Department. Rome, Italy.
2. Kinsey, N. and Walters, C. 2006. Neal Kinsey's Hands-On Agronomy: Understanding Soil Fertility & Fertilizer Use. Acres USA. 391 pp.
About Author / Additional Info:
I am currently pursuing PhD in Agricultural Economics from Punjab Agricultural University, Ludhiana.