Untangling the effects of shallow groundwater and soil texture as drivers of subfield‐scale yield variability

Abstract

Water table depth (WTD), soil texture, and growing season weather conditions all play critical roles in determining agricultural yield; however, the interactions among these three variables have never been explored in a systematic way. Using a combination of field observations and biophysical modeling, we answer two questions: (1) under what conditions can a shallow water table provide a groundwater yield subsidy and/or penalty to corn production?; and (2) how do soil texture and growing season weather conditions influence the relationship between WTD and corn yield?. Subfield-scale yield patterns during a dry (2012) and wet (2013) growing season are used to identify sensitivity to weather. Areas of the field that are negatively impacted by wet growing seasons have the shallowest observed WTD (<1 m), while areas with consistently strong yield have intermediate WTD (1-3 m). Parts of the field that perform consistently poorly are characterized by deep WTD (>3 m) and coarse soil textures. Modeling results find that beneficial impacts of shallow groundwater are more common than negative impacts under the conditions studied, and that the optimum WTD is shallower in coarser soils. While groundwater yield subsidies have a higher frequency and magnitude in coarse-grained soils, the optimum WTD responds to growing season weather at a relatively constant rate across soil types. We conclude that soil texture defines a baseline upon which WTD and weather interact to determine overall yield. Our work has implications for water resource management, climate/land use change impacts on agricultural production, and precision agriculture.

Scenarios reveal pathways to sustain future ecosystem services in an agricultural landscape

“…, Zipper et al. ). We used an updated version of Agro‐IBIS that included newly developed phosphorus and sediment modules; watershed‐scale phosphorus, sediment, and streamflow processes were carefully calibrated and evaluated against historical data with satisfactory performance (Motew et al.…”

“…Selected indicators capture key ecological processes that underlie the production or condition of each service (Qiu and Turner 2013). Agro-IBIS simulates continuous dynamics of terrestrial ecosystem processes, biogeochemistry, water and energy balance, and has been calibrated and validated extensively for performance in both natural and managed systems in the U.S. Midwest (Donner and Kucharik 2003, Kucharik and Twine 2007, Motew and Kucharik 2013, including recent studies focusing on subsurface water dynamics and agricultural production in the Yahara Watershed (Soylu et al 2014, Zipper et al 2015. We used an updated version of Agro-IBIS that included newly developed phosphorus and sediment modules; watershed-scale phosphorus, sediment, and streamflow processes were carefully calibrated and evaluated against historical data with satisfactory performance (Motew et al 2017).…”

Socio-environmental drought response in a mixed urban-agricultural setting: synthesizing biophysical and governance responses in the Platte River Watershed, Nebraska, USA

“…Annual yield residuals were compared to the countyaverage July 1-month SPEI for each year because drought during the critical pollination period have been shown to exert the largest impact on yield both in field studies (Hiler and Clark 1971, Çakir 2004, Boyer and Westgate 2004, Zipper and Loheide 2014, Zipper et al 2015 and nationwide . We calculated the annual ratio of corn planted area to wheat planted area as an indicator of farmer shifts from more water-intensive (corn) to low-water-use (wheat) crops, which we hypothesized would occur in response to drought conditions.…”

Simulation of root water uptake under combined soil moisture and salinity stress

“…In addition to water stress in periods of low water availability, root water uptake is also reduced when concentrations of soluble salts exceed plant-specific threshold values (Zipper et al, 2015). In irrigated soils, particularly in arid and semiarid regions, plants are generally subjected to both salinity and water stress.…”