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Unit 1: Basic Ecological Concepts and Principles Related to Agricultural Systems

Nutrient Cycling. As long as biotic factors related to climate and latitude remain constant, natural ecosystems tend to be self-sustaining; they are at equilibrium. Nutrients essential for plant growth are supplied through the decomposition and recycling of plant and animal wastes, a process resulting in little loss of nutrients. Because of this self-sustaining characteristic, a natural ecosystem is often called a closed system. In contrast, agroecosystems are considered open systems, since we regularly harvest and remove some product from the system. We cannot depend solely on the decomposition process to supply the nutrients for plant growth and reproduction; farmers usually add nutrients to maintain productivity and yields. A key question for agroecosystem managers is how to do that efficiently.