Agroecosystems stability in the argentine pampas

Abstract Consideration of yield stability seems to be especially relevant to agroecosystems that are exposed to environmental perturbations. Improved knowledge about agroecosystem structures and functions and their relationships to the surrounding environment is required. The three main purposes of this work were: (a) to improve knowledge about some ecosystem structures and functions; (b) to evaluate their effects on productivity and yield stability; (c) to consider the design of low cost alternatives to optimize output and minimize risk. By means of a time-sequence analysis, 145 productive periods each with an average duration of 14 consecutive years were considered. Yield oscillation along each time sequence offers an acceptable stability index for the analysed activities. By converting outputs to energy units, the yields and stabilities of different production activities were compared. Results indicate that environmental gradation of the Pampas region affects primary production of herbage and grain more than secondary production of milk and meat, and this effect increases as the environment becomes more restricted. Some combinations of farming activities and energy pathways appear to affect agroecosystem productivity and stability simultaneously. The role of diversification of activities as a tool for agroecosystem stabilization is analysed, and some results are presented. Finally, the perspectives of this agroecological approach to improve system designs and its adaptation to particular regional constraints, are discussed.