Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2008
Publication Date: 10/10/2008
Citation: Henry, A., Kleinman, P.J., Lynch, J.P. 2008. Phosphorus runoff from a phosphorus deficient soil under common bean (Phaseolus vulgaris L.) and soybean (Glycine max L.) genotypes with contrasting root architecture. Plant and Soil Journal. Available: http://www.springer.com/life+sci/plant+sciences/journal/11104. Interpretive Summary: Selection of crop species for rooting characteristics represents a major thrust of breeding programs geared toward helping low-input farmers in the developing world. A variety of root traits can improve the efficiency with which a crop recovers nutrients from the soil. For instance, better crop growth on nutrient-poor soils as a result in better canopy cover by a crop and lower erosion. Prompted by concern that the potential conservation benefits of root architecture were not adequately understood, scientists at Penn State and USDA-ARS conducted the first study of root trait effects on phosphorus losses in runoff. Differences in root architecture between common bean and soybean varieties did not significantly affect erosion or phosphorus loss in runoff, even though varieties with different root architecture did show significant differences in plant growth. The findings of this study indicate that root traits have little effect on phosphorus loss in runoff.
Technical Abstract: Selection of plant materials on the basis of root characteristics is key to improving nutrient and water use efficiency in low-input farming systems. Crop genotypes with superior root architecture can make more efficient use of available soil resources and, through improved growth, may also lower erosion. Little information exists, however, on the effects of root architecture on phosphorus (P) runoff, nor have the relative importance of root and shoot traits for soil erosion been quantified. Four genotypes of common bean (Phaseolus vulgaris L.) and two genotypes of soybean (Glycine max) with contrasting root architecture were established in an Aquic Fragiudult (less than 20 mg kg-1 Mehlich-3 P) and subjected to rainfall-runoff experiments with and without shoot removal. Plots with intact shoots yielded significantly less runoff (1.3-7.6 mm) and lower P loads in runoff (0.005-0.32 kg ha-1) than did plots with shoots removed (7.0-16.8 mm; 0.025-1.95 kg ha-1). Root lengths differed significantly among genotypes, but root length densities (0-15 cm) were less than. 4.0 cm cm-3 for all varieties. Variation in root length density was not correlated with runoff, erosion or P loss. Edaphic variability in P affected dissolved P in runoff, but plant sources did not. We conclude that for annual dicotyledonous crops such as bean and soybean with relatively low root length densities, root traits have little direct effect on P loss in runoff.