Economy


The economics of deficit irrigation Taking a thorough look and keeping an open mind. By George Oamek, PhD


R


ecently, Stephen Smith, PhD, FASIC, CAIS, CLIA, (Irrigation Today Editorial Board chair)


Times and technology have changed significantly over the life of the data we’ve been using.


sent me a draft of an article dealing with deficit irrigation. The article concluded that it may not be an economical practice. Stephen knows that I more or less agree with this conclusion but try to keep an open mind. With that, I have summarized my skepticism in this column and then shown remarkable inconsistency by stating that we should keep trying.


Deficit irrigation has long been identified as a mitigation measure for dealing with a


limited water supply. That is, irrigate with less


and hope that yields are not


reduced proportionately. A lot of scientific evidence demonstrates that precision irrigation at critical times of plant development achieves this, and several generations of agricultural economists have incorporated this concept in research and resulting master’s theses. Along with fallowing and changing cropping patterns, deficit irrigation is one of three methods identified for reducing agriculture’s consumptive use of water in a shortage environment. Deficit irrigation is a pretty sexy thing for an economist because it uses introductory calculus to illustrate “trade-offs at the margin” and is a great instructional concept to see the


relationship between water, yields and farm profit. The problem is that its economics haven’t worked in the past and don’t appear to work quite yet at a significant scale with traditional row crops.


My history with deficit irrigation goes back to the late 1970s and the Ogallala High Plains studies examining the impacts of declining aquifer levels. It is notable that similar measures are currently being studied in this area 40 years later — in some cases using the same data. As part of my predecessor’s and my own thesis, we used newly developed crop-water production functions that quantified crop yield responses to limited irrigation. Our limited calculus showed that applying a full irrigation to fewer acres and, in some cases, changing from irrigated corn to irrigated wheat, were the more profitable choices. I came to a similar conclusion 10 years later doing similar research in California’s Central Valley and have watched 20 years of graduate students testing the same relationships in the Plains states, often using the same crop- water response functions we used in the 1970s, but also supplementing it with more recent data developed at a U.S. Department of Agriculture Experiment Station on Colorado’s northern Front Range. So, the conclusions drawn in the recent article received from Stephen were no surprise.*


To further pile on the troubles with deficit irrigation, methods for insuring


* I’ll qualify this by confessing my lack of knowledge about recent split-season irrigation strategies being used for high mountain forages on Colorado’s Western Slope. Quantifiable savings are being leased by environmental interests for dedication to instream flow in the upper Colorado basin.


32 Irrigation TODAY | July 2018


a managed deficit irrigation crop while still recognizing the producer’s historical yields are still evolving. Also, it’s hard to manage — a high degree of precision and verification are required to make it a practical method for quantifying conserved water and leveraging it for other uses such as instream flows or municipal supply.


Despite this past skepticism, it’s worth continuing research. What? Times and technology have changed significantly over the life of the data we’ve been using, and new data reflecting evolving technologies is sorely needed. Drought-tolerant crop genetics and our abilities to measure things precisely have dramatically improved. Last year’s University of Nebraska Testing Ag Performance Solutions Program used new but economically available technology to demonstrate that managed deficit irrigation was just slightly less profitable than a full dose of water. It would be great at the farm level, and it will be interesting to see if they can maintain these results this year and next. The jury is still out whether we can translate these savings to transferable water in a practical manner, however. So, possibly deficit irrigation for Great Plains row crops is a method whose time has finally arrived. I’ll keep an open mind.


George Oamek, PhD, is


an economist with Headwaters Corp. and is also on the staff of the Platte River Recovery Implementation Program’s executive director’s office.


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