Soil Water and Temperature in Chemical Versus Reduced-Tillage Fallow in a Mediterranean Climate

Abstract

A 2-year rotation of winter wheat (Triticum aestivum L.)-summer fallow is a dominant cropping system in the dryland region of the Pacific Northwest United States. Traditional, tillage-based summer fallow relies on a soil mulch to disrupt capillary continuity to conserve seed-zone water for early establishment of winter wheat. However, tillage to create the soil mulch and to subsequently fertilize and control weeds often results in unacceptable levels of wind erosion due to the burial of crop residues and the exposure of fine soil particles. Chemical (no-till) fallow (CF) and reduced-tillage fallow (RT) are two alternatives for reducing wind erosion. Our objectives were: (i) to assess the effects of CF and RT on seed-and root-zone temperature and water regimes; and (ii) to 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 during April 2003-March 2004. The RT treatment was observed to retain more seed-zone water over summer compared to CF, consistent with relevant literature for Mediterranean environments and of critical importance to farmers. 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 the RT. SHAW-simulated water contents followed the general 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 (November-December) 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.

Minimum tillage and no-tillage winter wheat–summer fallow for low precipitation regions

“…The difference between our findings and those of Al-Mulla et al (2009) might well be the difference between our data collected over the course of two summers and their data collected for one spring, summer, autumn, winter, and early spring cycle. However, our results differed in other substantial points.…”

“…Dryland crop research in the low and intermediate precipitation zones of the Inland Pacific Northwest has largely focused on precipitation captured during the fallow year and the subsequent soil water storage through the hot and dry months of June, July, and August (Al-Mulla et al 2009;Schillinger 2001;Schillinger and Bolton 1993;Williams et al 2014;Wuest 2010). Soil water dynamics are controlled by soil texture, soil structure, differential vapor pressure, temperature, and interactive water and heat transport processes (Al-Mulla et al 2009). In soil where tillage destroyed structure, precipitation can be trapped at or near the surface and evaporate.…”

“…Sufficient autumn precipitation to replenish soil water for germination and establishment often does not arrive until late October to mid-November (Thorup-Kristensen et al 2009). In black-fallow or conservation tillage systems, breaking the capillary continuity to the soil subsurface conserves soil water with a tilled soil mulch through the summer, making seeding possible from mid-August and early September (Al-Mulla et al 2009;Schillinger and Bolton 1993).Winter wheat seeded this early in the crop cycle significantly outpro-duces mid-and late-fall seeding by up to 30% (Donaldson et al 2001), more so in the northern end of the region where growing degrees accumulate slower with substantially less precipitation (unpublished data comparing Echo, Oregon, with Lind, Washington). Thus, some producers continue to look for and evaluate variations on reduced tillage.…”

Effects of Climatic Conditions and Management Practices on Agricultural Carbon and Water Budgets in the Inland Pacific Northwest USA

“…The annual precipitation ranges from <200 mm to >600 mm from the west to the east of the iPNW region, resulting in different types of management practices because of water demands. Annual fallow and irrigation are two important management practices for dry areas in this region to provide sufficient water for farming (Al-Mulla et al, 2009;. In the iPNW region, 39% (1,557,000 ha) of croplands are fallow and 16% (646,000 ha) are irrigated (Schillinger, Papendick, & McCool, 2010).…”

First Leaf Emergence Force of Three Deep‐Planted Winter Wheat Cultivars

“…Precipitation in this region occurs mostly during winter. The deep planting method of farming, and its advantages and disadvantages, has been studied and documented in great detail (Papendick et al, 1973;Lindstrom et al, 1974;Hammel et al, 1981;Schillinger et al, 1998Schillinger et al, , 2017Schillinger and Young, 2004;Schillinger and Papendick, 2008;Al-Mulla et al, 2009;Wuest, 2010;Schillinger, 2011). Late summer planting of winter wheat (Triticum aestivum L.) into tilled fallow is common and frequently necessary for production of maximum yield (Donaldson et al, 2001;Higginbotham et al, 2013).…”