ROOTING CHARACTERISTICS OF CORN, SOYBEANS AND BARLEY AS A FUNCTION OF AVAILABLE WATER AND SOIL PHYSICAL CHARACTERISTICS

Abstract

Root densities of field-grown corn, soybeans and barley were measured as functions of depth in four soils of different textures for 1 yr, and root depths were monitored for 2 additional years. General relationships were established between root depth, available soil water and soil texture. Maximum root depths were found to be inversely related to available water within the limits imposed by crop rooting habits and soil physical characteristics. Roots continued to develop during the reproductive growth phase and maximum root densities were found about the time of physiological maturity. Root distribution with depth was described for each crop on each soil using a modified exponential equation with an extinction coefficient specific to crop, growth stage and soil. Reasonable estimates of root distribution can be predicted from root density in the top layer using a crop-specific extinction coefficient in this modified exponential equation. Key words: Maximum root density, root distribution, rooting depth, nonlinear fitting