Low participation rates by farmers in voluntary agri-environmental programs may depend on rationally bounded ex ante estimates of the negative effect of program enrollment on farm income. Uncertainty and the presence of information transaction costs may lead to the use of heuristics by farmers to reduce adoption decision costs. This paper describes how LENNART, a net-based decision support system (DSS), has been designed to exploit the use of heuristics and provide low cost access to information. The model has been developed to evaluate the effects of agronomic measures on farm income and on the leaching of nutrients from cultivated fields. A subsidy program for catch crop cultivation in Southern Sweden served as the basis for development of the DSS and is used throughout the paper for purposes of illustration. (C) 2004 Elsevier B.V. All rights reserved.