Root Distribution and Soil Moisture Depletion Pattern of a Drought‐Resistant Soybean Plant Introduction

Abstract

AbstractIn the southeastern USA, soybean [Glycine max (L.) Merr.] yield is often limited by water availability. Breeders have explored the use of exotic germplasm as a means of developing a root system capable of exploiting soil water reserves more fully. In this study, the drought‐resistant PI 416937 was compared with ‘Forrest’ for soil moisture utilization and root distribution on a Dothan loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudults). Water treatments (well‐watered and water‐deficient) were established during R4 to late R6 with rain exclusion shelters and differential irrigation. Soil moisture utilization in row and interrow areas was monitored via neutron attenuation and tensiometry. A direct measurement of root distribution was obtained on a second site by a trench profile technique. Results suggest that PI 416937's advantage may reside in its ability to exploit upper soil horizons (above 68 cm) with a network of fibrous roots. Localized measurements of soil moisture tension indicated that PI 416937's rate of soil desiccation was slower than Forrest's, but it appeared to exploit a larger total soil volume. Trench profile results indicated that the lateral spread of PI 416937's root system was greater than that of Forrest. The usefulness of PI 416937 may lie in the opportunity it provides soybean breeders for adding diversity to the root morphology of present soybean cultivars.