Soil water dynamics with spring camelina in a three-year rotation in Washington’s winter wheat-fallow region

Authors: Wuest, Stewart; SCHILLINGER, WILLIAM - Washington State University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2019
Publication Date: 9/26/2019
Citation: Wuest, S.B., Schillinger, W.F. 2019. Soil water dynamics with spring camelina in a three-year rotation in Washington’s winter wheat-fallow region. Soil Science Society of America Journal. 83(5):1525-1532. https://doi.org/10.2136/sssaj2019.05.0157.
DOI: https://doi.org/10.2136/sssaj2019.05.0157

Interpretive Summary: Camelina (Camelina sativa (L.) Crantz) is a short-season oilseed with tolerance to water stress and frost. Camelina has been promoted as a potential alternative crop for the low-precipitation region of the US inland Pacific Northwest where a winter wheat (Triticum aestivum L.)-summer fallow rotation is practiced by the vast majority of farmers. An 8-yr field experiment was conducted at Lind, WA to compare a 3-yr winter wheat—camelina—summer fallow rotation to the typical 2-yr rotation. Here we report a detailed analysis of soil water dynamics of these two crop rotations throughout the experiment. Growing spring-planted camelina reduced soil water content at the beginning of the fallow period, and this reduction resulted in an average of 21 mm less water at the time of winter wheat planting and a 170 kg ha-1 reduction in grain yield compared to the winter wheat—summer fallow rotation. We present evidence that: (i) the deep-rooted broadleaf weed Russian thistle (Salsola tragus L.) present in camelina most years was a likely reason for significantly greater in-crop soil water use, and (ii) the limited residue produced by camelina was likely responsible for greater evaporative loss during the spring-through-late-summer segment of fallow. We report the first findings from the Pacific Northwest drylands of greater water use by a spring crop versus winter wheat as well as greater evaporative loss during the dry summer months due to lack of residue in a minimum-tillage summer fallow comparison. In this experiment, extending the crop rotation to include camelina was costly in terms of water use, surface soil residue cover, soil water storage during fallow, and winter wheat grain yield.

Technical Abstract: Camelina (Camelina sativa (L.) Crantz) of the Brassicaceae family is a short-season oilseed with tolerance to water stress and frost. Camelina has been promoted as a potential alternative crop for the low-precipitation (<350 mm annual) Mediterranean-like climate region of the US inland Pacific Northwest where a monoculture 2-yr winter wheat (Triticum aestivum L.)-summer fallow (WW—SF) rotation is practiced by the vast majority of farmers. An 8-yr field experiment was conducted at Lind, WA to compare a 3-yr WW—camelina—SF rotation to the typical 2-yr WW—SF rotation. Here we report a detailed analysis of soil water dynamics of these two crop rotations throughout the experiment. Growing spring-planted camelina reduced soil water content at the beginning of the fallow period, and this reduction resulted in an average of 21 mm less water at the time of WW planting and a 170 kg ha-1 reduction in grain yield compared to WW—SF. Compared to WW—SF, we present evidence that: (i) the deep-rooted broadleaf weed Russian thistle (Salsola tragus L.) present in camelina most years was a likely reason for significantly greater in-crop soil water use, and (ii) the limited residue produced by camelina was likely responsible for greater evaporative loss during the spring-through-late-summer segment of fallow. We report the first findings from the Pacific Northwest drylands of greater water use by a spring crop versus WW as well as greater evaporative loss during the dry summer months due to lack of residue in a minimum-tillage SF comparison. In this experiment, extending the crop rotation to include camelina was costly in terms of water use, surface soil residue cover, soil water storage during fallow, and WW grain yield.