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Understanding Water Science

by Bob Glodt, Plainview Texas

Bob Glodt

Bob Glodt

This is my 34th year as an agricultural consultant on the Texas High Plains. As I look back over those years, I am amazed at the advancements that have taken place. The way producers farmed 34 years ago is certainly different from today. However, one thing that hasn’t changed over all these years is that water is a yield-limiting factor, and there is no substitute for water.

From 2006 to the present, I have been involved in working with seed companies in testing varieties or genetically modified cotton plants for wateruse efficiency on my research farm located in Hale County, Texas. I have learned a lot about water in the process of conducting these trials, and, as a result, my emphasis in consulting is now centered around helping my clients better understand the relationship between water and yields.

From working in water-use efficiency research, I have come to the unshakeable conclusion that regardless of where you farm in the United States, there is nothing a producer or an agricultural consultant can devote time to that is more important than understanding water use. More specifically, this would include the relationship between water and the soil and the relationship between water and crop demand. It does not matter where you farm or whether the majority of the water that nourishes your crop comes from rainfall, irrigation or a combination of both; the more you learn about water the better producer or consultant you will become.

So, if you want to take the first step, my advice would be to begin tracking potential evapotranspiration (PET) models for the crops you grow, regardless of where you farm. In the Texas High Plains, we are fortunate that the Texas Alliance for Water Conservation (TAWC) has developed a website (www.tawcsolutions.org) devoted entirely to this purpose. This website allows a producer to use the Texas Tech University Mesonet weather sites for developing potential evapotranspiration models for just about every production area in the Texas High Plains.

The Texas Alliance for Water Conservation had its first “water course” for producers in the spring of this year. TAWC currently has plans to implement a more detailed and comprehensive course on water management that will be available to producers in this region. I see the benefit of farmers learning the science behind water management before I can be effective in assisting them with the day to day water management decisions.

Since we have limited rainfall and limited irrigation reserves in this area, knowing precisely when or when not to apply water is crucial information. From working with water-use efficiency research, it has become clear to me that producers in my area should be irrigating cotton between 60 and 70 percent of potential evapotranspiration. Yep, you read that right. I advocate irrigating at a specific level that is well below 100 percent of crop demand. And the reason? We don’t accumulate enough heat units each year to irrigate at higher levels without a corresponding potential for immaturity when we receive our first killing freeze.

And how much can you make doing this? It is not uncommon to consistently produce between 2.5 and three bales per acre if you have a little help from Mother Nature. Also, when irrigating at 60 to 70 percent of PET, there are pre-bloom irrigation strategies that must be followed for this technique to be successful. Understanding the soil water-holding capacity is also extremely crucial when irrigating at any given percentage of potential evapotranspiration.

I have found that many producers in this area select cotton varieties based on trial results that were irrigated far above their capacity to irrigate. The highest yielding varieties under heavy irrigation are often not the highest yielding varieties when irrigated at 30, 50 or 60 percent of potential evapotranspiration. We are learning that it is important to grow a variety that will perform well at a specific or target irrigation level. In our area, seed companies are working hard to develop this type of information.

I also think it is high time that every major agricultural university in the United States offers comprehensive courses in water (water 101, 201, 301 and 401) for the agriculturalists who will serve farmers and the agricultural community in the future. If you want to better understand water as it relates to cotton production, a good place to start is reading an online article entitled, “How a Cotton Plant Grows.” Go to (http://www.extension.org/mediawiki/files/3/38/Cotpla ntgrows.pdf).

Contact Bob Glodt via email in Plainview, Texas, at agri@amaonline.com.