Henry,A., Kleinman,P.J.A. and Lynch,J.P.(2009): Phosphorus runoff from a phosphorus deficient soil under common bean (Phaseolus vulgaris L.) and soybean (Glycine max L.) genotypes with contrasting root architecture. Plant Soil, 317, 1-16.

『対照的な根構造をもつインゲンマメ（Phaseolus vulgaris L.）とダイズ（Glycine max L.）遺伝子型の下のリン欠乏土壌からのリン流出』

『Abstract
　The selection and breeding of crop genotypes with root traits that improve soil resource extraction is a promising avenue to improved nutrient and water use efficiency in low-input farming systems. Such genotypes may accelerate nutrient extraction (“nutrient mining”), but may also reduce nutrient loss via soil erosion by producing greater shoot biomass and by direct effects of root traits on aggregate formation and water infiltration. Little is known about the effects of root architecture on phosphorus (P) runoff and soil erosion, and the relative importance of root and shoot traits on runoff P loss has not been determined. Four genotypes of common bean (Phaseolus vulgaris L.) and two genotypes of soybean (Glycine max) selected for contrasting root architecture were grown in a low P soil (Aquic Fragiudult, ＜20 mg kg-1 Mehlich-3 P, 3％ slope) and subjected to rainfall-runoff experiments with and without shoot removal. Plots with intact shoots had significantly lower runoff volumes (1.3-7.6 mm) and total P loads in runoff (0.005-0.32 kg ha-1) than plots with shoots removed (7.0-16.8 mm; 0.025-1.95 kg ha-1). Dissolved reactive P leached from plant material did not contribute significantly to P loss in runoff. Total root length acquired from soil cores differed significantly among genotypes. Root length densities in the upper 15 cm of soil mid-way between rows were less than 4.0 cm cm-3 and variation in root length density was not correlated with runoff or P loss. Root length density also did not affect rainfall infiltration or surface runoff volume. 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 soil erosion.

Keywords: Phosphorus; Runoff; Erosion; Root architecture; Common bean』

Introduction
Materials and methods
　Experiment location and plant material
　Rainfall simulations
　Soil and root sampling
　Sample analyses
　　Soils
　　Plants (shoots and roots)
　　Runoff water
　Statistical analyses
Results
　Plant growth
　Runoff
　Erosion and particulate P in runoff
　Total dissolved P in runoff
　Root length density and runoff
Discussion
Conclusions
Acknowledgments
References

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