Crop selection in irrigated conditions entails characterization of crop water use and productivity dynamics under limited freshwater availability in a changing climate and environment. There is ample scope to optimally irrigate row crops, given the associated economic returns under full irrigation, and relatively non-alarming groundwater declines to require limited irrigation, at least in many parts of the United States, including Nebraska. However, a fair and careful comparative assessment of cereal row crops for their efficiency of water use and associated metrics under optimal growth conditions is lacking. We conducted field research in semi-arid south central Nebraska during 2016–2018 to comprehensively characterize water use and productivity dynamics in four major C3 (soybean and winter wheat) and C4 [maize (long season or L.S. and shorter season or S.S.) and sorghum] crops under consistent and well-managed conditions. Crop-specific signatures were found in seasonal profiles of total soil-water and soil-water depletion. The highest seasonal total evapotranspiration (ETa) was demonstrated by winter wheat (604 mm), followed by L.S. maize (594 mm), soybean (591 mm), S.S. maize (547 mm), and sorghum (518 mm). Normalization and scaling of ETa was accomplished so as to better reflect comparative ETa per unit of heat accumulation (thermal units or TU). ETa was also studied relative to evaporative demand using single and basal crop coefficients (Kc and Kcb, respectively). Consequently, empirical functions were developed for Kc and Kcb using base-scales of days after emergence, cumulative TU (CTU), and normalized CTU. Crop-specific sensitivity of Kcb to morphological area was studied. Crop water productivity based on grain yield (WPGY) and aboveground biomass (WPAGB) was quantified and it was found that the two C4 crops were 89% more water-efficient than their C3 counterparts. Finally, the importance of VPD to explain the variability and improve prediction of WPAGB in various crops was established.
All Science Journal Classification (ASJC) codes
- Agronomy and Crop Science
- Water Science and Technology
- Soil Science
- Earth-Surface Processes