ECONOMIC ANALYSIS APPROACHES TO POTATO-BASED INTEGRATED CROP SYSTEMS: ISSUES AND METHOD
In response to stagnating yields and mounting pest problems, Michigan potato growers are investigating ways to bring manure and cover crops back into potato production systems. The alternative systems bring benefits and costs for monetary net returns, the variability of net returns, and environmental impacts. This paper reviews the likely yield and biological system effects of alternative potato production systems that incorporate manure and cover crops. After briefly considering research designs for gathering experimental versus farm field data, it reviews four economic analysis methods for evaluating alternative systems. All methods are illustrated with examples. First, for evaluating comparative average profitability, it reviews a) enterprise budgets, b) partial budgets, and c) break-even analysis. Second, for integrating environmental impacts into profitability analysis by using monetary measures of environmental effects, it introduces "green" budgets. Third, for evaluating efficiency trade-offs between profitability and environmental impacts, it covers trade-off frontiers. Finally, for comparing the variability of returns across systems (including for risk-averse decision makers), it introduces analysis of variance and stochastic dominance. These methods provide a basic set of tools for the economic analysis of changes in potato-based crop systems that should be adequate for most static comparisons of annual crop management practices.
Cover crops as a means of ecological weed management in agroecosystems
Weeds cause an estimated crop yield loss of about 43% world-wide. The heavy use of herbicides in weed management has several environmental and health risks. Therefore, systems-oriented approaches to weed management that make better use of alternative weed management tactics need to be developed. One of these approaches is the use of plants with strong weed-suppressing abilities as a component of integrated crop management. Cover crops are well-suited in such a holistic approach as they provide many other agroecosystem services besides suppressing weeds. However, compared to the use of herbicides, the use of cover crops as a weed management tool needs careful follow-up throughout the intended period to maximize the agroecosystem services they provide, minimize the disservices they exert, and optimize their selectivity between weed and crop suppression. Although there are many review papers that address the contribution of cover crops for managing weed problems in agroecosystems, few systematically address the difficulties that are encountered in fitting in the cover crops in the different cropping systems and the methods how to overcome these difficulties. Therefore, this paper is to examine how to maximize weed suppressive effects of cover crops and minimize the negative side effects of introducing cover crops into annual and perennial cropping systems and how to optimize selectivity between weeds and crops. We suggest further research regarding the selection of cover crops that are compatible with annual and perennial cropping systems under different climatic conditions and identify the traits responsible for adaptation in various cropping systems and environments.
EFFECTS OF CROP ROTATIONS AND FERTILIZATION ON YIELDS AND QUALITY OF SPRING WHEAT GROWN ON A BLACK CHERNOZEM IN NORTH-CENTRAL SASKATCHEWAN
Effects of rotation length, crop sequence, and fertilization on yields and quality of spring wheat (Triticum aestivum L.) were examined for eight crop rotations over a 27-yr period (1960-1986) on an Orthic Black Chernozem at Melfort, Saskatchewan. The silty clay loam soil had an initial organic N content of about 0.55% (0-to 15-cm depth). During 1960-1971, fertilized plots received N and P based on general recommendations for the region; thereafter, fertilizer was applied based on soil tests. Yields of wheat grown on fertilized fallow were similar for fallow-wheat, fallow-wheat-wheat (F-W-W), and a 6-yr fallow-wheat-legume hay rotation (avg. 2519 kg ha−1 in 1960-1971 and 3036 kg ha−1 in the wetter 1972-1986 period). In contrast, yields of wheat grown on fertilized stubble in a F-W-W rotation (avg. 2113 kg ha−1 in 1960-1971 and 2775 kg ha−1 in 1972-1986) averaged 34% higher than yields of continuous monoculture wheat due to fewer observed weed and disease problems. Fertilized stubble wheat yields in F-W-W ...