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, A. - Kansas State University; AGUILAR, J. - Kansas State University; CURRIE, R. - Kansas State University; CIAMPITTI, I. - Kansas State University; VARAPRASAD, P. - Kansas State University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2018
Publication Date: 3/1/2019
Citation: Araya, A., Gowda, P.H., Golden, B., Foster, A.J., Aguilar, J., Currie, R., Ciampitti, I.A., Varaprasad, 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: Groundwater levels in the Ogallala aquifer have declined due to excessive pumping combined with relatively low recharge rates. This has greatly reduced water availability for irrigated agriculture in the region. To match the water availability with the crop water requirement for major crops in the region, producers may need to decrease irrigated area coverage, grow crops that are less water consumptive, and increase water productivity. In this study, a simulation study was conducted to improve our understanding on the relationships among irrigation capacity, crop water use, crop yield and net income for three major irrigated crops (winter wheat, grain sorghum and corn) in the southwest Kansas. Simulation results indicated that growing irrigated corn is more profitable than growing winter wheat or grain sorghum in the region. However, increase in irrigation demand for growing corn may not be sustainable considering fast depleting groundwater levels in the underlying Ogallala aquifer. Further, post-harvest costs such as storage and processing were not included in this study and thus, we recommend these costs to be included in future research.

Technical Abstract: Simulation studies were carried out to understand (i) relationships among irrigation/irrigation capacity (IC), yield, crop water use, and net income; and (ii) evaluate the effect of irrigation and irrigation capacity on irrigation water productivity, crop water productivity and net income for three major crops (winter wheat, grain sorghum and maize) in the southwest Kansas. The Decision Support System for Agrotechnology - Cropping System Model (DSSAT-CSM) calibrated and validated in a prior study was used for this purpose. Long-term (1950 – 2013) climate data was obtained from Garden City, KS. 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). Yield and crop evapotranspiration (ET) were simulated for calculating crop and irrigation water productivities. The relationship between yield and ET, irrigation and crop water productivity, IC and yield, and irrigation and net income were evaluated. The long-term simulation showed that winter wheat, grain sorghum and maize yield can be optimized under irrigation capacity of 1.7 – 2.5, 1.7 – 2.5 and 5 mm/day with corresponding irrigation application of 100-150, 100-250 and 450-500 mm, respectively. The crop and irrigation water productivities of winter wheat, grain sorghum and maize were ranged from 9.8–11.7, 13.8-17.3 and 12.7-17.2 kg/ha/mm and 3.5-11.8, 5.5-20.4 and 16.0-25.9 kg/ha/mm, respectively. Net income for winter wheat and grain sorghum grown under dryland condition could exceed $54/ha and $20/ha once every two years. However, growing winter wheat and grain sorghum under irrigation was not profitable due to increased production cost. In contrast, 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 average net income under 5 mm/day irrigation capacity for optimally irrigated maize could exceed $128/ha and $372/ha once every two and four years, respectively. However, this income and employment opportunities from growing maize may not last long due to fast depleting groundwater levels in the underlying Ogallala aquifer. This would mean, the short term profitability and employment opportunities need to be compared with the long-term environmental impact, food security and employment opportunities including sustaining the growing municipal and industrial water needs. In this study, post-harvest costs such as storage and processing were not included and thus, we recommend these costs to be included in future research.