Using Knowledge of Soil Nutrient Cycling Processes to Design Sustainable Agriculture

Perspectives from different but complementary schools of thought in ecology are being applied to sustainable agriculture-population and community ecology on one hand and ecosystem ecology on the other. These perspectives intersect in the study of mechanisms and controls of processes in ecosystems. Increased understanding of these processes in agroecosystems will contribute to development of sustainable agriculture. Current models of nutrient cycling in soil suggest that active or readily mineralizable fractions of soil organic matter (SOM) are coupled to plant-available nutrient pools through the processes of mineralization and immobilization. Factors that control these processes (soil temperature, water, and texture; and resource quality of organic inputs) are influenced by management practices and represent potential controlling points for managing nutrient cycles in agroecosystems. Organic inputs present different problems for nutrient management than & synthetic fertilizers, because most nutrients must be mineralized before they are available to plants. This extra link in the nutrient flow pathway adds uncertainty to nutrient management. However, this may reflect more our lack of understanding of processes involved than an inherent unmanageability of organic fertilizers. Further research is needed to determine longterm trends in organic matter processes in agroecosystems; to improve predictive capabilities of nutrient-cycling process models and linkages with landscape-scale models; and to determine relationships between biodiversity of soil biota and nutrient cycling processes in agroecosystems.