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Title: Developing and normalizing average corn crop water production functions across years and locations using a system model

item ANAPALLI, SASEENDRAN - Colorad0 State University
item Ahuja, Lajpat
item Ma, Liwang
item Trout, Thomas
item McMaster, Gregory
item Nielsen, David
item ANDALES, ALLAN - Colorad0 State University
item Halvorson, Ardell
item CHAVEZ, JOSE - Colorad0 State University
item HAM, JAY - Colorad0 State University
item FANG, Q - Qingdao Agricultural University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2014
Publication Date: 9/27/2014
Citation: Anapalli, S.S., Ahuja, L.R., Ma, L., Trout, T.J., McMaster, G.S., Nielsen, D.C., Andales, A.A., Halvorson, A.D., Chavez, J., Ham, J.M., Fang, Q.X. 2014. Developing and normalizing average corn crop water production functions across years and locations using a system model. Agricultural Water Management. 157: 65-77. DOI: 10.1016/j.agwat.2014.09.002.

Interpretive Summary: With increasing human population, the demand for fresh water for both urban consumption and crop production is increasing. In the evolving scenario, water available for irrigated crop production is declining alarmingly with time. Providing crops with the right amount of water at the right time to optimize water productivity of food crops holds the key to containing this issue for food security. In this context, ‘limited irrigation’ is viewed as a system of managing water supply to impose periods of predetermined ‘drought that can result in the most economic benefit for the water available. Crop yield responses to water use or applied irrigation (CWPFs) can provide essential information for planning limited irrigations and allocations of the limited water resources for optimum crop production. However, precipitation and other weather factors greatly vary the irrigation requirements from year to year at a location. Therefore, for planning purposes, the CWPFs need to be based on long-term yield responses to weather and applied irrigations at a location. We combined a dynamic process-oriented cropping system simulation model with short-term limited irrigation experiments and long-term weather data to develop long-term average CWPFs for corn at Greeley, Weld County; Akron, Washington County; and Rocky Ford, Otero County, Colorado. We were able to generalize the CWPFs across the soils and the three locations through linear relationships between grain yield and crop water consumptive use (ET). These relationships allow us to develop reasonable CWPFs for locations and soils where experimental data are not available for calibration/validation of the model to develop detailed long-term average functions.

Technical Abstract: Crop water production functions (CWPFs) are often expressed as crop yield vs. consumptive water use or irrigation water applied. CWPFs are helpful for optimizing management of limited water resources, but are site-specific and vary from year to year, especially when yield is expressed as a function of irrigation water applied. Designing limited irrigation practices requires deriving CWPFs from long-term field data to account for variation in precipitation and other climatic variables at a location. However, long-term data are seldom available. We developed location-specific (soil and climate) long-term averaged CWPFs for corn (Zea mays L.) using the Root Zone Water Quality Model (RZWQM2) and 20 years (1992-2011) of historical weather data from three counties of Colorado. Mean CWPFs as functions of crop evapotranspiration (ET), ET due to irrigation (ETa-d), irrigation (I), and plant water supply (PWS = effective rainfall + plant available water in the soil profile at planting + applied irrigation) were developed for three soil types at each location. Generalization, or scaling, of the developed CWPF across soils and climates was also developed. A Cobb-Douglas type response function was used to explain the mean yield responses to applied irrigations and extend the CWPFs for drip, sprinkler and surface irrigation methods, respectively, assuming irrigation application efficiencies of 95, 85 and 55 %, respectively. The CWPFs developed for corn, and other crops, are being used in an optimizer program to help farmers manage limited water for maximum farm profitability in Colorado.