Economic value and water productivity of major irrigated crops in the Ogallala aquifer region

Authors: ARAYA, ALEMIE - Kansas State University; Gowda, Prasanna; GOLDEN, BILL - Kansas State University; FOSTER, ANSERD - Kansas State University; AGUILAR, JONATHAN - Kansas State University; CURRIE, RANDALL - Kansas State University; CIAMPITTI, IGNACIO - Kansas State University; VARA PRASAD, P. - Kansas State University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2018
Publication Date: 2/1/2019
Citation: Araya, A., Gowda, P.H., Golden, B., Foster, A., Aguilar, J., Currie, R., Ciampitti, I., Vara Prasad, P.V. 2019. Economic value and water productivity of major irrigated crops in the Ogallala aquifer region. Agricultural Water Management. 214: 55-63. https://doi.org/10.1016/j.agwat.2018.11.015.
DOI: https://doi.org/10.1016/j.agwat.2018.11.015

Interpretive Summary: Ogallala aquifer is one of the largest freshwater aquifers used for irrigated agriculture in the U.S. Great Plains including southwestern Kansas. Groundwater levels in the Oglala aquifer are declining due to excessive pumping for irrigated agriculture. Currently, many of the wells in the Ogallala region are unable to generate irrigation capacities (IC) needed to meet crop water requirements, especially for maize. In this study, a crop growth model was used to evaluate crop water productivity and return on three major crops (winter wheat, grain sorghum and maize) in the southwestern Kansas. Long-term simulations showed that average yields of winter wheat, grain sorghum and maize can be stabilized with 100–150, 100–250 and 450–500 mm irrigation, respectively. The corresponding crop water productivities were ranged from 9.8–11.7, 13.8–17.3 and 12.7–17.2 kg/ha/mm. Maize was found to be profitable when grown under both deficit and full irrigation conditions, however, optimal irrigation application for maize substantially increased the net return. The median net return after variable cost (RAVC) for dryland wheat ($244/ha) and grain sorghum ($186/ha) was greater than that for irrigated wheat ($175–$193/ha) and grain sorghum ($105–$110/ha). For maize, the lowest and highest RAVC corresponded to IC of 2.5 ($284/ha) and 5 mm/day ($544/ha). However, this higher income from growing maize under higher IC may not be sustainable due long due to rapidly depleting groundwater levels in the underlying Ogallala aquifer.

Technical Abstract: Crop water productivity and return after variable cost for three major crops (winter wheat, grain sorghum and maize) in the southwestern Kansas were evaluated based on simulated yield using the Decision Support System for Agrotechnology - Cropping System Model (DSSAT-CSM). Winter wheat and grain sorghum were treated with four irrigation capacities (ICs) (zero, 1.7, 2.5 and 5 mm/day) while maize was treated with two ICs (2.5 and 5 mm/day). Long-term simulations showed that average winter wheat, grain sorghum and maize yields can be stabilized under 1.7–2.5, 2.5 and 5 mm/day ICs with corresponding irrigation of 100–150, 100–250 and 450–500 mm, respectively. The crop water productivities of winter wheat, grain sorghum and maize ranged from 9.8–11.7, 13.8–17.3 and 12.7–17.2 kg/ha/mm, respectively. Maize was found to be profitable when grown under both deficit and full irrigation conditions although optimal irrigation application for maize substantially increased the net income. The median net return after variable cost (RAVC) for dryland wheat ($244/ha) and grain sorghum ($186/ha) was greater than that for irrigated wheat ($175–$193/ha) and grain sorghum ($105–$110/ha). The RAVC for wheat and grain sorghum did not rise with increase in irrigation and IC, whereas the RAVC for maize increased with the increase in irrigation and IC. The lowest and highest RAVC for maize corresponded to IC of 2.5 ($284/ha) and 5 mm/day ($544/ha). However, this income from growing maize under higher IC may not last long due to rapidly depleting groundwater levels in the underlying Ogallala aquifer. Therefore, the short-term benefits of growing maize under higher ICs need to be compared with the long-term environmental impact, food security and employment opportunities including sustaining the growing municipal and industrial water needs.