In my career, I have had the privilege of working with cotton producers in the Mississippi Delta, the Coastal Plain of Georgia and the Southern High Plains of Texas. As you can imagine, crop production in these three very distinct regions of the U.S. Cotton Belt is quite different. Production practices, challenges and limitations all differ. There is, however, one common production-related thread (no pun intended) among these three regions. From semi-arid west Texas to tropical south Georgia, irrigation management remains a production challenge/limitation for producers.
You would think the simple question of when and how much to irrigate would be easy to answer. Rainfall, prevailing climatic conditions, soil type, water source, energy costs, type and condition of irrigation system and stage of crop development not only make the answer difficult, but a moving target. Understandably, the default option is to over irrigate. We all understand, however, this option is not sustainable for both environmental and economic reasons. Even in regions with limited water, the question remains, “When does it pay to irrigate”?
For me, irrigation is all about stress management (for the crop, not the producer). Too little irrigation may reduce yield while too much irrigation may delay crop maturity and reduce fiber quality. To maximize profit per unit of irrigation water applied, we need to monitor (or at least predict with some degree of accuracy) crop water deficit stress. This is where we find the large void in irrigation management. We cannot manage something we cannot monitor.
Several technologies have been developed to help us monitor or predict crop water deficit stress. I would be willing to bet with a few clicks of a mouse any producer can find daily potential evapotranspiration (ET) for his or her region. Potential ET is a mathematical model based on daily climatic conditions. There are many variants of this model. While they all tend to be very accurate in predicting daily potential ET, they do not tell us anything about crop water deficit stress.
Other technologies have been developed to monitor soil water status. These technologies tend to be difficult to install and manage. They will provide the user with a mountain of data, but the data are not necessarily repeatable or even interpretable.
An accurate and repeatable measure of soil water status would be a good indicator of crop water deficit stress. We are not yet there with currently available technologies that monitor soil water status.
Finally, there exist technologies to monitor plant water status. These technologies are generally accurate and repeatable. Unfortunately, they tend to be time consuming and somewhat technical. Just in the last year or so a new plant-based technology has become available that was developed by the USDA-ARS.
With this technology, crop water deficit stress is indirectly monitored through canopy temperature. The ability to measure canopy temperature is nothing new. This particular technology combines inexpensive and reliable infrared thermometry, cellular and data-logging technologies to produce a new system to continuously monitor crop water deficit stress. This technology may prove to be useful, at least for some producers.
In my opinion, the real key to successful irrigation management is knowledge. A good irrigator will have a working knowledge of irrigation systems, soil and plant water relationships, crop growth and development, crop production, crop physiology and, yes, new technologies. We all understand irrigation inputs are becoming more expensive. The corporate giants are currently working on new transgenic technologies intended to maintain or increase yield with less water. The fact that these giants are willing to invest so heavily in this idea says something about where they believe irrigation costs are headed. I teach a class in crop water management at Texas Tech. I tell my students to look for the day when irrigation consulting for crops becomes a viable business. I believe it is headed our way.
Contact Craig Bednarz at (806) 742-1631 or via email at firstname.lastname@example.org or email@example.com.