Optimal rotation of peanuts and cotton to manage soil-borne organisms
Damage from the root-knot nematode (Meloidogyne arenaria) and Southern blight (white mold) fungus (Sclerotium rolfsii) are principal yield-limiting factors in the production of peanuts (Arachis hypogaea) in the USA. Both are widespread in the southeastern USA and yield losses caused by them can be severe. Both organisms can be suppressed by pesticides, but both can also be suppressed by rotation with cotton and certain other crops. This article presents a stochastic dynamic programming model that maximizes the expected present value of profit over a multi-year planning horizon with production of peanuts and cotton, accounting for: (1) the stochastic population dynamics of the peanut root-knot nematode, Southern blight fungus, and beneficial microbivorous nematodes; (2) the stochastic market prices for cotton and peanuts; and (3) land use in each of the previous 2 years. Expected profit from this seven-state variable dynamic programming model is compared to expected profit for monoculture peanuts, monoculture cotton, three fixed rotations, and a myopic, but flexible, rotation. Comparison of expected returns for these decision models indicates that an information-based strategy - the optimal dynamic strategy or the myopic strategy is better than any of the fixed rotations. The myopic strategy results in expected profits almost as high as the optimal strategy for this particular problem. Since a myopic strategy is much more easily computed and more easily explained to producers, it has much more promise for adoption than difficult-to-understand results from a stochastic dynamic programming model.
Taylor, CR; Rodríguez-Kábana, R
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