Soil water infiltration after oilseed crop introduction into a Pacific Northwest winter wheat-fallow rotation.

Authors: Williams, John; Reardon, Catherine - Kate; Wuest, Stewart; Long, Daniel

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2020
Publication Date: 10/6/2020
Citation: Williams, J.D., Reardon, C.L., Wuest, S.B., Long, D.S. 2020. Soil water infiltration after oilseed crop introduction into a Pacific Northwest winter wheat-fallow rotation. Journal of Soil and Water Conservation. 75(6):739-745. https://doi.org/10.2489/jswc.2020.00165.
DOI: https://doi.org/10.2489/jswc.2020.00165

Interpretive Summary: Maximizing water storage in the soils of the semi-arid Pacific Northwest requires rapid water infiltration. Tap-rooted crops are sometimes credited with improving water infiltration in the dryland croplands in similar regions. In a study repeated in three years, we tested whether adding one brassica crop (mustard or canola) to the traditional wheat--summer fallow rotation would improve water infiltration. We used ponded ring infiltrometers to measure infiltration and found substantially faster infiltration rates following brassica species (canola (1.99 inches per hour) and mustard (1.71 inches per hour) compared to following winter wheat (1.40 inches per hour). Root channels did not appear to be related to greater infiltration rates. We did not detect a significant effect of improved water infiltration or a rotation effect on the yield of the following spring wheat crop. Whether infiltration benefits would increase with repeated cycles of brassica in rotation was not determined.

Technical Abstract: Rapid water infiltration is important for improving water storage in arid and semi-arid areas. Tap-rooted crops are sometimes credited with improving water infiltration. In a study repeated in three years, we tested whether adding one brassica crop to the traditional wheat -- summer fallow rotation would improve water infiltration. We found substantially faster ponded water infiltration rates following brassica species (canola (50.54 ±31.81 mm hr-1) and mustard (43.37±28.33 mm hr-1) compared to following winter wheat (35.66±25.69 mm hr-1). Root channels did not appear to be the cause of greater infiltration rates, so we attribute the difference to greater surface aggregation. We did not detect a significant effect of improved water infiltration or a rotation effect on the yield of the following spring wheat crop. Whether infiltration benefits would increase with repeated cycles of brassica in rotation was not determined.