The Early Effects of Short-Term Grassland Set-Asides on the Physical Properties of Agriculture Soils.

Set-asides have shown the potential to remediate agriculture soils by relieving compaction and improving structure. The Grassland Set-Aside Stewardship (GLSA) program is a unique program in Canada, which provides cost-share payments to growers for placing fields under an unmanaged grass and legume restoration mix for a 1-4 year period. Growers typically place degraded sites into GLSA to improve soil properties, however, the benefits of these short-term set-asides on soil properties are still not well understood. The objective of this study was to evaluate the changes in soil physical properties after 1 and 2 seasons of GLSA establishment relative to (1) the GLSA pre-establishment soil conditions and (2) adjacent regularly managed cropped fields containing either Potatoes, Beans or Grain. Nine sites containing both a GLSA and adjacent crop field were sampled for aggregate stability, bulk density, aeration porosity and mechanical resistance during the 2015 and 2016 growing seasons. Sampling was conducted three times each season with a pre-planting (baseline in 2015), mid-season and post-harvest assessment. Preliminary data showed differences in soil properties between the crop and GLSA fields at the 2015 post-harvest assessment. The average mean weight diameter (MWD) of water stable aggregates at the 0-7.5cm depth was higher in GLSA (2.23 ± 0.24mm (SE)) than cropped fields (1.98 ± 0.17 mm). During this same assessment, bulk density was lower, and aeration porosity was higher in the GLSA at all three depths sampled (0-7.5cm, 7.5-15cm and 15-30cm). When comparing the varying crop types to their paired GLSA fields, the management for potatoes appeared to be most destructive to all three measured soil properties. Following harvest, the MWD for potatoes was significantly lower than the paired GLSA fields and bulk density was significantly higher at the 15-30cm depth. The results suggest that fields in the GLSA program have improved soil physical properties after a single season of establishment in comparison to fields managed for certain crop types.