ECONOMIC-MODELS AND BREEDING STRATEGIES FOR SOYBEAN IMPROVEMENT

Increasing concern about seed protein and oil in U.S. soybeans (Glycine max [L.] Merr.) by buyers, processors, and farmers dictate that soybean breeders give increased emphasis to chemical composition of soybean germplasm and cultivars. The evolutionary path of soybean improvement has been one of increasing seed yield and oil and decreasing seed protein. Breeding strategies to increase seed protein of U.S. soybeans have been proposed, including the adoption of minimal levels of protein for new cultivar releases. The task is difficult, however, because soybean seed protein and oil are highly negatively correlated and seed yield is usually negatively correlated with protein. Models have been proposed to determine the economic value of soybeans on the basis of seed oil and protein to aid in development of more equitable end-user value. The objectives of this paper are: (i) to compare three models proposed for estimating the economic value of soybeans; (ii) to specify the limitations of economic models as soybean selection and cultivar evaluation indices; and (iii) to evaluate proposed breeding strategies to increase soybean seed protein of U.S. soybeans. The models were compared by using a data set provided by the authors of one of the models and an additional hypothetical data set of soybean genotypes ranging from high oil-low protein to low oil-high protein. The three models gave similar dollar values per bushel and indentical rankings of economic value. All three models are adequate for selection and cultivar evaluation indices, but require an assumption of the future soybean oil:44% protein soybean meal price ratio. The National Oil-seed Processors Association's (NOPA) Standard Specifications for 44% protein soybean meal are minimums of 44% protein and 0.5% fat and maximums of 7.0% fiber and 12.0% moisture, with no provision for premiums for protein in excess of specifications. The economic model used must provide a proportionate premium for meal protein above NOPA's Standard Specifications for 44% protein soybean meal to justify the development of high protein soybeans. Adopting minimum levels of seed protein is not a desirable breeding strategy to improve the competitiveness of U.S. soybeans. If a minimum level of protein has to be imposed in soybean improvement, the minimum level should be on the meal protein rather than on seed protein.