Phosphorus runoff from a phosphorus deficient soil under common bean (Phaseolus vulgaris L.) and soybean (Glycine max L.) genotypes with contrasting root architecture

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.

Phosphorus in pasture plants: potential implications for phosphorus loss in surface runoff

“…The remaining three-quarters of P lost in surface runoff came from topsoil either via dissolution or erosion of particles, and potentially, plant roots. However, Henry et al (2009) found that compared to soil P, root architecture did not affect the P concentration in surface runoff. Mundy et al (2003) added weight to the hypothesis that recently grazed material was a considerable source of P to runoff by showing about twice as much P was lost in outwash from flood irrigation of a pasture mown to 43 mm compared to uncut pasture.…”

Production of Phaseolus vulgaris L. Genotypes with Tithonia diversifolia (Hemsl.) Gray and Cajanus cajan (L.) Millsp.

“…However, bean yields continue to be low in Central America, due to poor soil P availability [5]. Bean genotypes that can efficiently use soil P reserves have played a significant role in improving food security in this region [6]. Lynch [7] found that efficient bean genotypes have greater root mass, root length and root/shoot ratio, and their roots demonstrated an extraordinary ability to sense and respond to localized changes in P availability.…”

Evaluation of biological control potential of locally isolated antagonist fungi against Fusarium oxysporum under in vitro and pot conditions

“…In the present study the chlorophyll a+b content was found to be increased significantly in all treated plants as compared to FOP alone inoculated control. Previous reports suggested that applying biological control agents to infected plants increase mineral levels [(nitrogen (N), phosphorous (P), potassium (K) and magnesium (Mg)], chlorophyll biosynthesis and photosynthetic activity (Mahmoud et al, 2004;Henry et al, 2009;Morsy et al, 2009).…”