BIOPHYSICAL CONSTRAINTS AND ECOLOGICAL COMPATIBILITIES OF DIVERSE AGROECOSYSTEMS
Résumé
A diagnostic approach based on multi-scale integrated analysis and model simulations was employed to identify specific or common biophysical constraints, technological changes and ecological compatibilities of the diverse subsistence (SUB) and organic (ORG) agro-ecosystems in the Fertile Crescent (FC) of West Asia and the organic and conventional (CNV) agro-ecosystem in the Northern Corn Belt (NCB) and Northern Great Plains (NGP) of the U.S. For each agro-ecosystem, soil carbon, total yield, temporal yield variance and yield coefficient of variation per crop rotation were used as sustainability indicators. Thresholds of technologies necessary for the proper functioning and flow of agro-ecosystem services were identified under the most-likely IPCC-projected climate change scenarios for the next 30 years. The carbon budgets of agro-ecosystems were largely related to the choice of crops, crop sequence, and length of the crop rotation, and were influenced by external inputs, tillage system and removal of crop residues. Carbon depletion is expected to be less in organic and subsistence agro-ecosystems when nitrogen-fixing legumes are included in more diverse crop rotations and when crop residues are incorporated into the soil. Potential nutrients loss to the environment was significantly larger in conventional systems, and nutrients are expected to be depleted over time in subsistence- faster than in organically-managed soils. Optimal and sustainable agricultural intensification is feasible through agroecosystem diversification and the proper integration of genetic and natural resources management. In all agroecosystems, for more diverse rotations to be adopted at a large scale, there needs to be large and easily accessible markets for the additional products
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