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The non-limiting water range (NLWR): An approach for assessing soil structure - Soil Quality Evaluation Program Report 2

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Title: The non-limiting water range (NLWR): An approach for assessing soil structure - Soil Quality Evaluation Program Report 2
Author: Topp, G. C.; Galganov, Y. T.; Wires, K. C.; Culley, J. L. B.
Abstract: The Non-Limiting Water Range (NLWR) has been measured for eight Canadian soils using a combination of both field and laboratory methods. Infiltration and redistribution in the field, monitored with TDR and tensiometers, gave the upper part of the desorption curve. A friction sleeve penetrometer determined cone resistance of soil cores equilibrated to matric potentials between 0 and -1500 kPa. The intent was to assess the NLWR as an indicator of soil physical quality. When viewed relative to available water capacity, the NLWR was found to indicate trends in soil physical condition showing that long term or intense cultivation regimes have contributed to a decline in soil structural quality. Over 90% of the soil horizons tested developed > 2 MPa penetrometer resistance above matric potentials of -1500 kPa. Less than 50% of the horizons showed inadequate aeration porosity. Many field crops were able to extract water to well below the water content having 2 MPa penetration resistance. In some cases the crops extracted water to below -1500 kPa. NLWR values were reported from cores only as there were some instances of unexplained discrepancies between field and laboratory water content measurements at -10 kPa. The NLWR is a useful integrator parameter and its wide-spread use will depend both on additional assessments of the limiting values for both aeration and soil strength in relation to plant response and also on being able to estimate the NLWR limits from other more readily available soil parameters.
Date: 1994
Rights: In Copyright - Non-Commercial Use Permitted
Rights Holder: Agriculture and Agri-Food Canada
Related Publications: G.C. Topp, Y.T. Galganov, K.C. Wires and J.L.B. Culley. 1994. Non-limiting water range (NLWR): an approach for assessing soil structure. Soil Quality Evaluation Program Technical Report 2. Centre for Land and Biological Resources Research, Agriculture and Agri-Food Canada, Ottawa, ON. 36 pp.

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