Evaluating Physical Condition of Kumamoto Soil Based on the “Non —Limiting Water Range” Concept

Abstract

Soil Physical Properties related to root growth have been diagnosed by measuring separately air porosity, available water, gas diffusion, mechanical impedance etc. However, these factors interrelatedly and affect crop growth. The optimum physical condition for crop grow th may be that non- limited by soil water, aeration, and mechanical resistance. NLWR., proposed by Letey, seems superior diagnosis of soil physical conditions because of considering these factors comprehensively. These relationships were demonstrated using I)/Do 0.02 and soil strength 12kgf/cm2 as limiting values with main upland soils of Kumamoto prefecture. As the results, reasonable correspondance between N.LWR and experiential productivity.and correlation (r=0.71)between NLWR water content and root length of wheat were found.