LOWER LIMIT OF AVAILABLE WATER FOR 3 PLANT-SPECIES GROWN ON A MEDIUM-TEXTURED SOIL IN SOUTHWESTERN SASKATCHEWAN

Numerous researchers estimate and report laboratory-determined lower limit of available water contents using - 1.5 MPa water potentials. For medium-textured soils, laboratory-measured lower limits should be determined at potentials of at least -4 MPa, and possibly - 10 MPa, when using pressure membrane procedures. However, because the lower limit of available water is dependent upon environmental, plant and soil factors, we agree with Ratliff et al. (1983) that field-measured lower limits are preferable to laboratory-measured lower limits. Field-measured lower limits of available water did not vary markedly between spring wheat, alfalfa and grass.