Irrigation Strategies Pair Water-Use Efficiency With Profit
Rainfall and/or access to irrigation water is essential to viable cotton production. Circumstances vary across the different regions of the Cotton Belt. Some areas are plagued by drought and declining aquifers, whereas other areas that typically receive a generous amount of rainfall may not receive it when needed during the growing season. When the latter happens, cotton farmers rely on pivot irrigation or furrow irrigation to supply water to the crop.
Knowing how to interpret data from water efficiency tools and practices as well as taking crop growth stage into consideration are important factors in achieving successful irrigation strategies. University researchers are one group in the cotton industry who has put a lot of effort and resources into evaluating technology and ways of producing a cotton crop, and then communicating their findings and recommendations to producers.
Following are examples of their efforts to conserve water and maintain profits within the cotton irrigation arena.
Variable-Deficit Irrigation Helps Improve Yields, Save Water
⋅ BY KAY LEDBETTER ⋅
TEXAS A&M AGRILIFE
Cotton producers struggling with available water after drought and dropping water tables can maximize crop yields from limited water with some planning and implementation of variable-deficit irrigation, according to research by Texas A&M AgriLife Research scientists.
A team of TAMU researchers recently published “Evaluation of Growth-Stage-Based Variable-Deficit Irrigation Strategies for Cotton Production in the Texas High Plains” in the Agricultural Water Management journal.
“This study is receiving a lot of attention from area producers who are trying to maximize their limited water,” said Dr. Srinivasulu Ale, AgriLife Research agrohydrologist at the Texas A&M AgriLife Research and Extension Center at Vernon and the Department of Biological and Agricultural Engineering.
“Results from this modeling study provide useful recommendations on appropriate irrigation management strategies for sustaining cotton production under different weather conditions while conserving valuable groundwater resources of the Ogallala Aquifer.”
Ale was joined on the study by his former postdoc Dr. Sushil Himanshu and current postdoc Dr. Sayantan Samanta, AgriLife Research, Vernon.
Also on the team were Dr. Jourdan Bell, Texas A&M AgriLife Extension Service agronomist, Amarillo; Jim Bordovsky, retired AgriLife Research agricultural engineer, Halfway; and former postdoc Dr. Yubing Fan. The U.S. Department of Agriculture Agricultural Research Service laboratory at Lubbock was represented by Dr. Dennis Gitz and Dr. Robert Lascano and at Bushland by Dr. David Brauer.
About The Study
The study simulated four irrigation deficit levels in four cotton growth stages, resulting in 256 scenarios. The goal was to identify efficient growth-stage-based variable-deficit irrigation, GS-VDI, strategies based on data from cotton irrigation water-use efficiency field experiments conducted by Bordovsky at the Texas A&M AgriLife Research Center at Halfway.
The four growth stages were:
• First leaf to first square.
• Flower initiation to early bloom.
• Peak bloom.
• From cutout to late bloom to boll opening.
The long-term simulations reflected conditions from 1977-2019 and were conducted with four deficit levels — 30%, 50%, 70% and 90% evapotranspiration replacements.
Dry, Normal And Wet Years
Based on the results of simulated seed cotton yield and irrigation water-use efficiency, Ale and his team concluded that different efficient GS-VDI strategies should be considered for dry, normal and wet years.
For example, a strategy of 90% evapotranspiration-replacement from first leaf to peak bloom and of 30% evapotranspiration-replacement in the final stage was found to be an ideal strategy in normal precipitation years to achieve higher seed cotton yield while saving 2.56 inches of irrigation water.
Overall, the flower initiation/early bloom and peak bloom growth stages were the most sensitive stages to water stress. The cutout, late bloom and boll opening growth stage was the least sensitive to water stress and water deficit, so yield and water-use efficiency were not significantly affected.
“We also found that the amount of irrigation water required to achieve maximum irrigation water-use efficiency was less than the amount of irrigation water required to achieve maximum seed cotton yield under all weather conditions,” Himanshu said. “By adopting GS-VDI strategies, a substantial amount of irrigation water can be saved, and it is possible to achieve high seed cotton yields with less irrigation water.”
Texas High Plains Region
Bell said the results indicated that the extent and timing of water deficit stress in different cotton growth stages substantially affected seed cotton yield, irrigation water use and water-use efficiency.
The results from this study could be useful for producers in the Texas High Plains region in optimizing the application of limited available irrigation water to achieve higher irrigation water-use efficiency and cotton yields.
“We believe producers can go into a normal cotton season with a strategy of 70% deficit in the fourth stage and 10% deficit in the remaining stages,” Ale said. “Our future efforts will focus on simulating the effects of GS-VDI strategies at different sites across the High Plains region to strengthen the recommendations.”
Water Conservation Is High Ag Priority At MSU
⋅ BY BONNIE A. COBLENTZ ⋅
MISSISSIPPI STATE UNIVERSITY
Agriculture is the world’s single largest consumer of fresh water, making the water shortages expected over the next 10 years in at least 40 states — Mississippi included — critically important.
The Nature Conservancy estimates 70% of the planet’s freshwater withdrawals annually are for agriculture. In the United States, irrigation accounts for more than 80% of total water use.
“Each year, Mississippi growers add 40,000 to 50,000 more acres of irrigation,” said Jason Krutz, director of the Mississippi Water Resources Research Institute, or MWRRI, at Mississippi State University.
Although Mississippi has one of the highest precipitation rates in the country, much of that rain falls outside the growing season. Crops are watered using two main methods: pivot irrigation, where water is sprayed from overhead sprinkler systems; or furrow irrigation, where water is released in large quantities to flow down furrows between crop rows.
Correct Use Of Technology
Through the water institute and the National Center for Alluvial Aquifer Research, MSU is heavily invested in promoting water conservation and irrigation efficiency while maintaining farm yields. Since 2012, the university has dedicated extensive research efforts and countless manhours finding best irrigation practices and extending that information to the agricultural producers of the state.
“We are looking at the technology, tools and approaches to irrigation to make it as effective and efficient as possible,” Krutz said.
MSU efforts primarily focus on the adoption and correct use of soil moisture sensors, which make it possible to schedule irrigation efficiently, and the use of computerized hole selection and surge valves so water in furrow irrigation is dispersed at the appropriate rate.
Water conservation and financial savings are equally important, said Dave Spencer, an Extension pivot irrigation specialist.
“We have shown water savings up to 40% and yield improvement up to 5% when these technologies are properly implemented,” Spencer said.
That means growers who adopted water efficiency tools and practices reduced water use by up to 40% and still saw slight improvements in crop yields.
Soil Moisture Sensors
Soil moisture sensors are key tools in irrigation efficiency.
These sensors are strategically placed underground to measure the amount of moisture in the soil at the plant’s root zone. Knowing how much water is actually available to the plant allows the grower to postpone irrigation even if the top of the ground is very dry.
Soil moisture data also allows growers to accurately predict how many days remain before water is needed, allowing them to postpone irrigation if rain is likely in the forecast, Spencer said.
Mississippi has a 20% adoption rate for soil moisture sensors, a close second to Nebraska. The regional and national average is less than 2% adoption. These tools are not enough unless the grower knows how to interpret the data and make decisions based upon it.
“There’s still 80% that we can work with,” Spencer said. “We’re looking at production systems holistically and evaluating production systems to see how to use the irrigation technologies with the greatest efficiency.”
A Farmer’s Endorsement
Jeremey Jack, owner of Silent Shade Planting Co. in Belzoni, has adopted irrigation efficiency tools, including the scheduling of irrigation.
“We have the mindset of conservation,” Jack said. “Last year on row rice, we had wells come on and off automatically. We treated rice like a golf course where irrigation was on a schedule, and we would adjust that from our phone if it was going to rain. We would go by every couple of days to make sure the well was working.”
Jack said his farm does not focus on just one tool, but constantly learns new strategies and methods that can increase profitability through higher yields while conserving resources.
“So many things have improved through the practices we’ve been able to implement through technology,” he said.
Strike A Good Balance
⋅ BY PHILLIP EDWARDS, DAVID HALL, DANIEL LYON, JASON MALLARD AND WES PORTER ⋅
UNIVERSITY OF GEORGIA
Based on planting observations and crop development, most farmers’ crop should fall within the first square to first flower stage throughout the month of June. If you were unfortunate and did not get your cotton planted until later May or early June, then your crop will fall into the emergence to first square stage. Crop water requirements increase dramatically from squaring and flowering. From 30 days to 50 days after planting, water consumption almost doubles.
Keep this in mind as we move into middle and late June, and into early July. Don’t fall behind on your irrigation once the crop reaches squaring and into flowering. As a reminder, typically as water use increases in late June through July, usually so does very hot and dry weather. Bear this in mind and stay on top of your irrigation applications. Conversely, don’t over-irrigate the crop as there are yield penalties for doing so.
If you have been using soil moisture sensors, be sure you are utilizing sensors on the probe according to how the root system has developed as it reflects current crop water use in the profile. Root growth and water usage will dramatically increase at deeper depths as the cotton moves through squaring and into bloom during mid to late June and early July. As we move through the season, we will need to be more balanced as the season progresses and root growth increases.
One last consideration, top dressing all cotton and our first dose of growth regulator on aggressive, irrigated growing cotton will soon or has already taken place. Don’t go into this stage with the mindset of “I’m going to hold back on the water now because I don’t want it to take off.” If proper growth regulator is applied, it will prevent vegetative growth as it should. If rain chances are low, irrigation will be required to get the fertilizer in the plant by irrigating it in and allowing the plant to uptake the nutrients. For further questions about mid-season cotton irrigation management, contact your local county Extension agent.