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United States Department of Agriculture

Agricultural Research Service

Title: Soil Water and Temperature in Chemical versus Reduced-Tillage Fallow in a Mediterranean Climate

Authors
item Al-Mulla, Yaseen - SULTAN QABOOS UNIV, OMAN
item Wu, Joan - WASHINGTON STATE UNIV
item Singh, Prabhakar - WASHINGTON STATE UNIV
item Flury, Marcus - WASHINGTON STATE UNIV
item Schillinger, William - WASHINGTON STATE UNIV
item Huggins, David
item Stockle, Claudio - WASHINGTON STATE UNIV

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 2008
Publication Date: December 1, 2009
Repository URL: http://hdl.handle.net/10113/28790
Citation: Al-Mulla, Y.A., Wu, J.Q., Singh, P., Flury, M., Schillinger, W.F., Huggins, D.R., Stockle, C.O. 2009. Soil Water and Temperature in Chemical versus Reduced-Tillage Fallow in a Mediterranean Climate. Applied Engineering in Agriculture. Vol. 25(1): 45-54.

Interpretive Summary: Establishing winter wheat in the dryland Pacific Northwest requires soil water at depths that the seeds are planted in the early fall. Usually, a soil mulch is created and maintained to conserve seed-zone water and to promote the early establishment of winter wheat. Unfortunately, the tillage used to create the soil mulch often results in unacceptable levels of wind erosion. Chemical (no-till) fallow (CF) and reduced-tillage fallow (RT) are two alternatives for reducing wind erosion, but their effectiveness in maintaining sufficient seed-zone water is unknown. Our objectives were to: (i) assess the effects of CF and RT on seed- and root-zone temperature and water; and (ii) test a model (Simultaneous Heat and Water, SHAW) for simulating management effects on soil temperature and water. Weather data, soil temperature, and water content were monitored in CF and RT treatments. The RT treatment was observed to retain more seed-zone water over summer compared to CF. During the wet winter, CF gained more water than RT. Observed soil temperatures were higher in the CF than in RT. SHAW-simulated water contents followed the trend of the field data, though it slightly under-predicted soil water content for CF and over-predicted for RT. We concluded that RT would provide more seed-zone water for winter wheat establishment than CF. In addition, the SHAW model proved adequate in simulating soil water and temperature, and therefore may serve as a useful modeling tool for evaluating tillage and residue management alternatives.

Technical Abstract: A rotation of winter wheat-summer fallow is a dominant cropping system in the dryland region of the Pacific Northwest. Traditional, tillage-based summer fallow relies on a soil mulch to conserve seed-zone water for early establishment of winter wheat. However, tillage to create the soil mulch often results in unacceptable levels of wind erosion. Chemical (no-till) fallow (CF) and reduced-tillage fallow (RT) are two alternatives for reducing wind erosion. Our objectives were to: (i) assess the effects of CF and RT on seed- and root-zone temperature and water regimes; and (ii) test the Simultaneous Heat and Water (SHAW) model for simulating management effects on soil temperature and water. Weather data, soil temperature, and water content were monitored in paired CF and RT treatments. The RT treatment was observed to retain more seed-zone water over summer compared to CF. During the wet winter, CF gained more water than RT because of later planting of winter wheat, and thus less water use. Observed soil temperatures were higher in the CF due to its lower dry soil albedo, higher bulk density and thermal diffusivity than in RT. SHAW-simulated water contents followed the trend of the field data, though it slightly under-predicted soil water content for CF and over-predicted for RT. SHAW under-predicted soil temperature during the dry summer and over-predicted for the wet winter period yet the overall trend was properly described with differences between simulations and observations decreasing with soil depth. Overall, SHAW proved adequate in simulating seed-zone and whole profile soil water and temperature, and therefore may serve as a useful modeling tool for tillage and residue management.

Last Modified: 9/23/2014
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