Productivity and water use efficiency of intensified dryland cropping systems under low precipitation in Pacific Northwest, USA

Authors: Williams, John; Reardon, Catherine - Kate; LONG, DANIEL - Volunteer

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2020
Publication Date: 4/10/2020
Citation: Williams, J.D., Reardon, C.L., Long, D.S. 2020. Productivity and water use efficiency of intensified dryland cropping systems under low precipitation in Pacific Northwest, USA. Field Crops Research. 254. https://doi.org/10.1016/j.fcr.2020.107787.
DOI: https://doi.org/10.1016/j.fcr.2020.107787

Interpretive Summary: Crop production in the rainfed semiarid interior Pacific Northwest (U.S.) is principally limited by a lack of water. Traditionally winter wheat (WW) has been grown here in a cycle of fall seeding, summer harvest, followed by 14 months of fallow involving two to six tillage operations (SF). Tillage management and crop cycle diversification and intensification have been shown in similar regions to improve precipitation capture and soil water storage, and subsequently productivity. The objective of this study was to compare crop yield, water use efficiency, rain and snow melt (precipitation) capture, and soil water storage between SF and a reduced tillage fallow (RTF), wherein one tillage operation was performed preceded by and followed with herbicides to control weeds. Eight rotations were evaluated over a 5-yr period, WW-SF, WW-RTF, WW-spring barley (SB)-RTF, and winter canola (WO)-spring wheat-RTF. Ponded infiltration rates, used to evaluate precipitation capture, were statistically higher in 2-yr rotations managed with RTF (3.05 inches per hour) than SF (1.50 inches per hour). Despite this difference, we did not find significant or substantial differences in soil water recharge or depletion between RTF and SF. Variation in seasonal precipitation was the main determinate of water use and WUE. RTF managed winter wheat yields (43 bushels per acre) and water use efficiencies (12 pounds per acre per inch precipitation) were higher following fallow that that of winter triticale (27 bushels per acre/ 8 pounds per acre per inch precipitation) and winter canola (11 bushels per acre/ 3 pounds per acre per inch precipitation). Water use and productivity of spring crops following these winter crops in 3-yr rotations were higher following fallow. Establishing spring barley or spring carinata as rotation crops with winter wheat will increase diversification, improve conservation of water, and suppress weeds that in turn will reduce input costs and increase biological sustainability.

Technical Abstract: A lack of plant available water limits the ability to diversify the summer fallow-winter wheat rotation in low precipitation areas of the inland Pacific Northwest (PNW). The objective of this study was to compare crop yield, water use efficiency, precipitation capture, and soil water storage between SF and RTF and among different 2-yr and 3-yr cropping sequences. Eight rotations were evaluated over a 5-yr period, winter wheat (WW)-summer fallow (SF), WW-reduced tillage fallow (RTF), WW-spring barley (SB)-RTF, WO-spring wheat-RTF. Ponded infiltration rates were significantly higher (P=0.05) in 2-yr rotations managed with RTF (77.68±24.56 mm/hr) than SF (37.08±13.03 mm/hr). Despite this difference, we did not find significant or substantial differences in soil water recharge or depletion between RTF and SF. Variation in seasonal precipitation was the main determinate of water use and WUE. RTF managed winter wheat yields (2901.60±1127.94 kg/ha) and water use efficiencies (348.52±29.04 kg/ha/mm) were higher following fallow that that of winter triticale (1809±288.07 kg/ha/ 215.56±17.96 kg/ha/mm) and winter canola (748±522.31 kg/ha/ 78.39±6.53 kg/ha/mm). Water use and productivity of spring crops following these winter crops in 3-yr rotations were higher following fallow. Establishing spring barley or spring carinata as rotation crops with winter wheat will increase diversification, improve conservation of water, and suppress weeds that in turn will reduce input costs and increase biological sustainability.