How efficiently do corn‐ and soybean‐based cropping systems use water? A systems modeling analysis

Abstract

Agricultural systems are being challenged to decrease water use and increase production while climate becomes more variable and the world's population grows. Low water use efficiency is traditionally characterized by high water use relative to low grain production and usually occurs under dry conditions. However, when a cropping system fails to take advantage of available water during wet conditions, this is also an inefficiency and is often detrimental to the environment. Here, we provide a systems-level definition of water use efficiency (sWUE) that addresses both production and environmental quality goals through incorporating all major system water losses (evapotranspiration, drainage, and runoff). We extensively calibrated and tested the Agricultural Production Systems sIMulator (APSIM) using 6 years of continuous crop and soil measurements in corn- and soybean-based cropping systems in central Iowa, USA. We then used the model to determine water use, loss, and grain production in each system and calculated sWUE in years that experienced drought, flood, or historically average precipitation. Systems water use efficiency was found to be greatest during years with average precipitation. Simulation analysis using 28 years of historical precipitation data, plus the same dataset with ± 15% variation in daily precipitation, showed that in this region, 430 mm of seasonal (planting to harvesting) rainfall resulted in the optimum sWUE for corn, and 317 mm for soybean. Above these precipitation levels, the corn and soybean yields did not increase further, but the water loss from the system via runoff and drainage increased substantially, leading to a high likelihood of soil, nutrient, and pesticide movement from the field to waterways. As the Midwestern United States is predicted to experience more frequent drought and flood, inefficiency of cropping systems water use will also increase. This work provides a framework to concurrently evaluate production and environmental performance of cropping systems.

Biomass sorghum and maize have similar water-use-efficiency under non-drought conditions in the rain-fed Midwest U.S.

“…WUE, EY, and EWR were higher for both species in 2015, likely due to greater SWtot, GDD, and precipitation in 2015, relative to 2014. Interannual variability in WUE was explained by different biomass accumulation between growing seasons, rather than changes in total ET, which is consistent with findings in the literature (Steduto et al, 1997;Narayanan et al, 2013;Hao et al, 2014;Dietzel et al, 2015). While both species had similar total ET, the pattern of ET accumulation within the season (Fig.…”

Modeling Long-Term Corn Yield Response to Nitrogen Rate and Crop Rotation

“…Our specific objectives were to: (a) quantify model prediction accuracy before and after calibration, and report calibration steps; (b) compare crop model-based techniques in estimating optimal N rate for corn; and (c) utilize the calibrated model to explain factors causing year to year variability in yield and optimal N. The APSIM model was selected for use in this study because of its flexibility and easy use in specifying crop rotations via the user interface, capability in simulating long-term dynamics in both soil and crop processes, advanced flexibility in simulating the effect of shallow water table dynamics that are important in this geographic region (Helmers et al, 2012) and previously determined good performance in this geographic region (Malone et al, 2007; Hammer et al, 2009; Lobell et al, 2013; Archontoulis et al, 2014a,b, 2016; Basche et al, 2016; Dietzel et al, 2016; Martinez-Feria et al, 2016). …”

Portable canopy chamber measurements of evapotranspiration in corn, soybean, and reconstructed prairie

“…The COBS field was established in 2008, and there are 24 plots (61 m by 27 m) and 6 cropping systems on Webster (fine-loamy, mixed, superactive, mesic Typic Endoaquolls) and Nicollet (fine-loamy, mixed, superactive, mesic Aquic Hapludolls) soils. The 6 zero-till cropping systems include corn-soybean, soybean-corn, continuous corn, and continuous corn with winter rye (Secale cereale) cover crop, reconstructed mixed prairie (C3 grasses, C4 grasses, legumes, and multi-functional group mixtures), and fertilized reconstructed mixed prairie (Daigh et al, 2015;Dietzel et al, 2015b;Jarchow et al, 2015). Measurements were made in 4 replications of 3 cropping systems (corn and soybean in corn-soybean rotation system, and reconstructed mixed prairie).…”