Characterization of the Least Limiting Water Range of Soils
- A. P. da Silva ,
- B. D. Kay and
- E. Perfect
The supplies of O2 and water and the mechanical impedance of soil are determined by soil structural form and soil water content. The range in soil water content in which limitations for plant growth associated with matric pressure, aeration, and mechanical resistance are minimal was defined as the least limiting water range (LLWR). This study was carried out to evaluate the LLWR as an index of the structural quality of soils. Undisturbed soil cores were taken from the 5- to 10-cm depth of a silt loam and a loamy sand, cropped to corn (Zea mays L.) and red clover (Trifolium pratense L.). Soil water retention, soil resistance, air-filled porosity, and bulk density (Db) were measured. Water contents at critical limits associated with field capacity (−0.01 MPa), wilting point (−1.5 MPa), air-filled porosity (10%), and soil resistance (2.0 MPa) were predicted and the LLWR calculated for each measured Db. The natural variation in Db on both soils gave rise to a wide variation in LLWR. Values of LLWR varied from 0 to 0.14 cm3 cm−3 for the silt loam soil and from 0.05 to 0.13 cm3 cm−3 for the loamy sand soil. At Db above 1.36 g cm−3 for the silt loam and 1.43 g cm−3 for the loamy sand, the LLWR declined sharply with increasing bulk density. Further research relating LLWR to crop response is required before LLWR can be recommended as a soil structural quality index for crop production.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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