Donald W. Lybecker

GWM: General weed management model

Abstract GWM is a decision support system designed for evaluating soil-applied and post-emergence weed management options in row crops. It has a general structure to allow use with different crops. The system consists of a simulation model, databases, and a database management module. The simulation model has a set structure for linking processes of weed population dynamics during a single season, but allows flexibility in how each process is modeled. Databases store model prameters, information about management options, and field-specific simulation inputs. The database management module allows a user to specify entirely the simulation model or modify existing versions without programming. GWM has been parameterized to evaluate weed management as in two existing models (WEEDSIM and WEEDCAM) and for dry bean production. The structure of GWM and associated databases appears to capture essential aspects of weed biology influencing management decisions. GWN can be enhanced as knowledge of weed biology and ecology is refined.

Bioeconomic Models of Crop Production Systems: Design, Development, and Use

Bioeconomic models describe biological processes and predict the effects management decisions have on those processes. Bioeconomic models are used to improve understanding of complex production systems, to assess the effects of policies and new technologies, and to support farm-level decisions. This article examines design objectives for bioeconomic models of crop production and the implications of design objectives for model structure and function, technical challenges associated with bioeconomic model development, and problems and opportunities related to the use of bioeconomic models for direct support of crop production management decisions.

MODELING THE ALFALFA STEM NEMATODE IN IRRIGATED ALFALFA

Abstract An alfalfa growth simulation model, modified to incorporate the impact of the alfalfa stem nematode and include an economic analysis component, is reported. The modified model was calibrated for Colorado growing conditions and used to evaluate nematode control measures and determine the optimal time for alfalfa replacement when fields are infested with the alfalfa stem nematode. The results indicate that planting nematode-resistant varieties increases returns from nematode-infested alfalfa fields. Nematode control activities implemented at the proper time can extend the economic life of an alfalfa stand. Planting a non-host crop in the fifth year of production also increases returns.

RURAL SUPPLY COOPERATIVE CAPITAL BUDGETING DECISION CASE: FEASIBILITY STUDY OF AUXILIARY ENTERPRISES FOR A RURAL SUPPLY COOPERATIVE

This capital budgeting case evaluates the feasibility of adding an auxiliary enterprise to a feed milling operation that an agricultural supply cooperative is considering purchasing. Both quantitative and qualitative objectives are taken into consideration regarding the cooperatives financial position, community employment, and farm level feasibility.