Metadata
To enhance farmer capacity in Delta to adapt to the expected changes in shoulder season
precipitation, a two year project was launched in collaboration between the University of British
Columbia and the Delta Farmers Institute. This project’s specific objectives were to:
1. Demonstrate and evaluate new on-farm strategies for addressing drainage and salinity
problems
2. Improve producer understanding of existing drainage and salinity management options
3. Increase producer access to drainage and salinity management information and tools
and promote promising strategies
In the fall of 2015, we established a trial on a field in Delta with known drainage and salinity
problems to demonstrate and evaluate the benefits of various drainage management practices.
To assess the efficacy of current drainage systems we sampled and monitored fields across
Delta with different drainage systems for two of the most prominent crops. Twenty-six fields (15
vegetables, 11 blueberry) were included in this study. These field data were then used to
parameterize and validate both field and landscape level digital soil maps and a drainage model
to predict soil workability for expected future rainfall patterns.
In our field-scale trial we found that both increasing drainage spacing and planting grassland
set-asides (GLSAs) had a moderate impact on soil moisture that did not immediately translate
into additional workable days. In the cropped fields (fields without GLSA), decreasing drainage
spacing from 60 to 30 feet had a small impact on soil moisture; installing a GLSA with 30 ft
drains had a small impact, and decreasing spacing in the GLSA from 30 to 15 ft had a moderate
impact. Tilling in a one-year GLSA in the fall had a large impact on soil moisture compared to
fields which remained in GLSAs at the same drain spacing.
Analysis of vegetable and blueberry fields sampled across Delta’s landscape highlighted the
variability in soil properties across the region and current conditions and performance of
drainage management. No differences were observed in bulk density regardless of drainage
management, indicating that at least at the soil surface, fields without drainage are not having
more problems with compaction. Nor were there differences observed in soil organic carbon
(SOC) indicating that drainage is not yet contributing to SOC losses. The fields that were
monitored across the landscape in Delta showed that current drainage systems increased
‘observed workable days’ by 8% in vegetable fields (14% with pumps) but did not decrease
ponding. In blueberry fields drainage systems lowered water table by 14% (22% with pumps)
and decreased ponding by 39% (83% with pumps). Across both vegetable and blueberry fields
we saw no impacts of drains on salinity. Based on our results however, we can clearly
recommend pumps if they can be installed to effectively remove water from the hydraulic
system of the field.
After one year, drain cleaning tended to increase workable days by 7% (although not
significantly) and lowered the water table by 13% (marginally significant). Drain cleaning did not
reduce salinity after one year. Additional sites and longer monitoring would be required to
determine for how long this drain cleaning benefit is effective and under what conditions it is
most likely to improve tile performance.
Modelling, based on parameterization from one year of field data from the field-scale trial,
predicted important differences between tile spacings for current and future precipitation. In
2030, based on predicted rainfall from climate models, our drainage model predicted many
fewer workable days than 2016 in general, and a much larger impact of drainage. Fields with
drains spaced at 15 ft had 64% more workable days and drains spaced at 30 ft had 46% more
workable days than fields without drains; a difference of 11 days gained from 15 vs. 30 feet.
Modeling clearly indicates the increased importance of drainage under an expected scenario of
increased shoulder season rainfall.
precipitation, a two year project was launched in collaboration between the University of British
Columbia and the Delta Farmers Institute. This project’s specific objectives were to:
1. Demonstrate and evaluate new on-farm strategies for addressing drainage and salinity
problems
2. Improve producer understanding of existing drainage and salinity management options
3. Increase producer access to drainage and salinity management information and tools
and promote promising strategies
In the fall of 2015, we established a trial on a field in Delta with known drainage and salinity
problems to demonstrate and evaluate the benefits of various drainage management practices.
To assess the efficacy of current drainage systems we sampled and monitored fields across
Delta with different drainage systems for two of the most prominent crops. Twenty-six fields (15
vegetables, 11 blueberry) were included in this study. These field data were then used to
parameterize and validate both field and landscape level digital soil maps and a drainage model
to predict soil workability for expected future rainfall patterns.
In our field-scale trial we found that both increasing drainage spacing and planting grassland
set-asides (GLSAs) had a moderate impact on soil moisture that did not immediately translate
into additional workable days. In the cropped fields (fields without GLSA), decreasing drainage
spacing from 60 to 30 feet had a small impact on soil moisture; installing a GLSA with 30 ft
drains had a small impact, and decreasing spacing in the GLSA from 30 to 15 ft had a moderate
impact. Tilling in a one-year GLSA in the fall had a large impact on soil moisture compared to
fields which remained in GLSAs at the same drain spacing.
Analysis of vegetable and blueberry fields sampled across Delta’s landscape highlighted the
variability in soil properties across the region and current conditions and performance of
drainage management. No differences were observed in bulk density regardless of drainage
management, indicating that at least at the soil surface, fields without drainage are not having
more problems with compaction. Nor were there differences observed in soil organic carbon
(SOC) indicating that drainage is not yet contributing to SOC losses. The fields that were
monitored across the landscape in Delta showed that current drainage systems increased
‘observed workable days’ by 8% in vegetable fields (14% with pumps) but did not decrease
ponding. In blueberry fields drainage systems lowered water table by 14% (22% with pumps)
and decreased ponding by 39% (83% with pumps). Across both vegetable and blueberry fields
we saw no impacts of drains on salinity. Based on our results however, we can clearly
recommend pumps if they can be installed to effectively remove water from the hydraulic
system of the field.
After one year, drain cleaning tended to increase workable days by 7% (although not
significantly) and lowered the water table by 13% (marginally significant). Drain cleaning did not
reduce salinity after one year. Additional sites and longer monitoring would be required to
determine for how long this drain cleaning benefit is effective and under what conditions it is
most likely to improve tile performance.
Modelling, based on parameterization from one year of field data from the field-scale trial,
predicted important differences between tile spacings for current and future precipitation. In
2030, based on predicted rainfall from climate models, our drainage model predicted many
fewer workable days than 2016 in general, and a much larger impact of drainage. Fields with
drains spaced at 15 ft had 64% more workable days and drains spaced at 30 ft had 46% more
workable days than fields without drains; a difference of 11 days gained from 15 vs. 30 feet.
Modeling clearly indicates the increased importance of drainage under an expected scenario of
increased shoulder season rainfall.
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