Heat- and water-stressed corn needs extra management
Record drought and air temperatures in the Texas Panhandle are causing a water deficit for corn, pushing producers to make some tough decisions, according to Texas AgriLife Extension Service specialists.
Practically all of the corn grown in the region is irrigated, typically requiring 18 to 24 inches of annual irrigation water to fully meet the water demand of the crop, according to Brent Bean, Ph.D., AgriLife Extension agronomist.
From the period of May 1 to June 26, total corn irrigation has been 13.2 inches, or 3.9 inches more than the previous six-year average, Bean said. Through June, much of the corn in the Panhandle has experienced up to a 7-inch deficit.
"Assuming a producer had the irrigation capacity to meet the increased water demand of 7 inches through June, increased pumping costs alone would add up to an additional $35 per acre," he said.
In areas with moderate irrigation capacity, corn and cotton have become a very common crop rotation with seasonal water splitting, said Nich Kenny, AgriLife Extension irrigation specialist.
"During multiple conversations this season, considerations for abandoning the riskier crop to ensure a more water- and heat-stress tolerant cotton crop have been expressed," Kenny said. "This is a difficult decision since both crops offer exceptional economic benefits under current market conditions."
Daily corn water use during the two weeks prior to and following silking over the last six years has been 0.34 inches, Bean said. But if weather conditions remain extreme, average water use during this time is expected to exceed 0.4 inch per day for extended periods.
Producers should keep this in mind as they determine their irrigation strategy during this critical time period, he said. Historically, producers have relied on stored soil moisture to get through the high water-use period during July and August.
"Drought and the abnormally high water demand during May and June have left many corn fields with less than ideal soil moisture storage as the crop is approaching its peak physiological water-use period," he said.
Producers basically have two corn management options if soil moisture is currently lacking and irrigation capacity is not sufficient to meet average daily water use of at least 0.34 inches or 6.5 gallons per minute/acre, Kenny said.
The options are to irrigate acres at less than full water use demand or strategically abandon a portion of corn acres to allow the remaining acres to be adequately irrigated, he said.
In areas north of the Canadian River where cotton has successfully been established, Kenny said water should exclusively be applied to the corn crop and the decision to abandon should be deferred until early to mid-July while the cotton crop is developing.
If no significant rainfall occurs prior to mid-July, serious consideration should be given to abandoning some corn acres for cotton or reduce overall corn target yields and focus on cotton, he said.
This decision is much more difficult in areas south of the Canadian River where heat and water stress are more prevalent and irrigation capacities are generally lower, Kenny said. It may be wise to begin splitting water earlier and targeting lower grain yields and/or abandoning crops.
Bean and Kenny offer some considerations for producers to use in helping make the decision on when and whether to abandon a crop. That information can be found at: http://amarillo.tamu.edu/files/2010/11/heat-waterstressed1.pdf.
If the decision is made to abandon some corn acres, the abandoned corn does have a value for silage or hay, Bean said. In a trial last year, the nutritional value of just-tasseled corn was similar to headed sorghum/sudangrass.
"It is recommended that pricing of the abandoned forage be secured prior to making the decision to abandon grain and economics be heavily considered in the final decision," he said. "Also, corn tends to be high in nitrate. Be sure and have it tested before feeding."