Root-zone soil moisture redistribution in cropping systems under freeze-thaw conditions
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Date
2008
Authors
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Publisher
University of Manitoba
Abstract
The availability and distribution of soil moisture within the root zone is a key
factor in ensuring better crop growth performance and attaining improved yield. The soil
moisture is influenced by farm management practices such as cover cropping that affect
the freeze-thaw processes during the fall. This in turn may influence accumulation and
redistribution of soil moisture during the winter, and thereafter, the soil’s response to
thawing during spring, and availability of soil moisture for the subsequent season. The
impact of cover cropping systems on soil temperature, infiltration, and soil moisture
redistribution due to soil freezing and thawing was investigated. In addition, the effect of
cover crop on the within-season and subsequent-season crop performance and yield was
also investigated. Time Domain Reflectometry (TDR) and Neutron Scattering (NS)
methods were used to measure the unfrozen and total water contents, respectively. Soil
temperature was measured using thermocouples embedded in the soil profile. Soil
moisture and soil temperature data were collected from August 2005 to September 2007.
Laboratory calibration of the TDR miniprobes indicated the maximum cable
length for the RG-58 50 Q coaxial cable to be 40.0 m when 35 mm TDR miniprobes
were used. Since the TDR was found to overestimate the liquid water content at soil
temperatures below 25°C, a method to correct the field measured TDR soil moisture for
temperature effects was developed.
During soil freeze-up, water from unfrozen soil layers below the freeze front
migrated towards frozen layers above. Compared to non-cover crop treatment, the cover
crop treatment did not freeze earlier during the fall, froze to a shallower depth during the
i
Description
Keywords
Soil Moisture, Cropping Systems, Freeze-Thaw Conditions