Technical VS. economic effectiveness of agricultural conservation practices

摘要

Agricultural activities contribute to both point and diffuse sources of environmental pollution, but activities leading to soil erosion from diffuse sources are arguably the largest contributor. Many conservation technologies have been demonstratedto be effective in curbing erosion and diffuse pollution, yet voluntary adoption and usage rates by North American farmers remain low. A complex set of technical, economic, sociological and institutional reasons seems to underpin this low usage rate. Soil conservation practices are of three main types: conservation tillage; conservation crop rotations; and conservation structures. Representative practices for each group are evaluated in this study for a Great Lakes system watershed. The study approach is to compare conservation practices with existing practices in the watershed. Technical comparisons are based on resource usage rates, crop yields, and soil erosion rates at the farm level, and on downstream watercourse pollution impacts at the societallevel. Economic comparisons are based on crop production costs, revenues and profits at the farm level, and on public benefits and costs of pollution prevention or amelioration at the societal level. From the study findings, it was observed that: While all conservation practices were effective in reducing soil erosion rates, not all practices under all circumstances reduced sediment and phosphorus loadings into watercourses; Although all practices were technically effective, only conservation tillage practices were profitable to farmers, and then only under specific crop production and management circumstances; Those conservation practices that produced the greatest benefit to society technically, did not provide a net benefit economically, because thehigh on-farm costs exceeded the societal benefits from improved water quality; Some practices with lower societal benefits technically produced overall economic benefits because on-farm costs of adoption and usage were lower than off-farm benefits, or because on-farm profits were generated. It was concluded that differences between technical effectiveness and economic effectiveness render it difficult to judge the efficacy of some agricultural practices; secondly, that one must link directly the conservation practices at the farm field scale with the pollution amelioration consequences at the societal watershed scale; and thirdly, that economic effectiveness measures should encompass public benefits and costs of conservation programs, as well as on-farm benefits and costs.