A late January cotton meeting with 10 University of Arizona agricultural scientists plus farmers, pest control advisors, and crop consultants resembled a ‘crop care clinic’ — chock-full of various crop issues and maladies combined with prescribed solutions for ailments.

The UA-sponsored meeting held in Avondale, Ariz. (West Phoenix), included a water-based discussion by Ed Martin, UA irrigation specialist, Tucson, Ariz. Martin opened the spigot for discussion on ever tightening water supplies in Arizona agriculture and potential ways to help cotton producers more efficiently utilize water in cotton production.

A day earlier, Martin attended a conference where participants discussed the next 100 years of water use in Arizona. The discussion centered on how Arizona can ensure adequate water supplies for its residents if Arizona’s ongoing drought continues.

Agriculture was discussed as the “buffer” to guarantee future water supplies, Martin says. When it comes down to a water shortage, it was suggested that some agricultural sectors could be closed down and started back up once the shortage was over.

Martin says Arizona received a good snow pack last winter plus good snowpack across the Colorado River basin. 

“Overall, Arizona agriculture is probably alright this year in available water for crops,” Martin said. “There are a few exceptions; mostly those growers who depend on the San Carlos system. Unless the snowpack increases this spring, we will likely face a water deficit situation next year.”

Most irrigation water inefficiencies in cotton occur early in the season mostly due to distribution methods along with application rates and amounts. This is especially true with surface water delivery.

Martin says alternate row irrigation (ARI) is a potential way for farmers to more efficiently water cotton. The ARI practice is traditionally used to control salt levels in the soil.

In Martin’s 2006-2008 ARI trials at the Maricopa Agricultural Center, one cotton furrow was irrigated and the next row was left dry. Conclusions from the study suggest farmers can reduce overall water use with ARI and still maintain yields.

“Alternate row irrigation can reduce water use,” Martin said. “While we irrigate 50 percent of the field, the total application amount is not reduced by 50 percent. Since we irrigate every other row, we are in fact only irrigating half the field, although we supplied water for the entire crop. Surprisingly, yields were maintained with ARI.”

In the trials, cotton seed was traditionally irrigated up above the seed line. After emergence, 8 to 12 inches of water is typically applied to the crop. With ARI, an initial irrigation of 3 inches was followed one to two weeks later with another 3-inch shot of water.

“We significantly reduced the amount of water we applied,” Martin said. “Plants need a certain amount of water and ARI met the plant’s water requirements.”

The tail end of the irrigated row is left open which allows water to enter the dry furrow for 10 feet to 15 feet to help control water if needed.

“Overall, we saved about 7 inches of water annually over the three-year trial,” Martin said. “With the price of water and how those outside of agriculture are eyeing agricultural water for city use, the water savings could be fairly significant for agriculture.”