A tendency to plant more crop than available water makes careful water applications scheduling vital this year, said a Texas Cooperative Extension specialist.
“What you really want to do is get the water to the crop,” said Leon New, Extension irrigation specialist in Amarillo. “You have a certain amount of water to pump, and you decide what crop or crops you're going to put it toward.”
With a good soil-moisture profile helping to get things started, producers should use weather station data gathered by the Texas High Plains Evapotranspiration Network, New said. This information, combined with their known irrigation capacity, will help meet daily crop water needs.
The weather station network, found at http://txhighplainset.tamu.edu/, compares four planting dates and has 17 weather stations each located 40 miles to 50 mile apart, he said. The data collection began in 1995, which provides a good representation of the way the weather has affected crops especially cotton — in this region.
“Pick the planting date nearest yours and look at the heat units,” New said. “It tells you what water requirements you are trying to meet. You determine if you want to or can meet the daily water deficits. You can risk a little more this year than last year because of the 6 inches or more of soil moisture stored from winter rain and snow.”
A well that pumps 3 gallons per minute per acre will allow an application of 1.10 inches a week, he said. Corn will require 21 to 22 inches of irrigation and a total of 32 to 34 inches of water for the growing year, while cotton will take 10 to 11 inches of irrigation with a total of 23 to 24 inches of water for the growing year.
Cotton as needed
With corn prices as high as they are, New said producers may want to plant a lot of corn, but switch to cotton where they don't have the 5.5 gallons per minute per acre necessary for corn.
Fuel prices are better than last year, and while there is no more water to pump, soil moisture is excellent, he said. Because irrigation doesn't have the capacity to meet all water needs, some has to come from soil moisture and rainfall.
Heat units come from July to September, when most of the crop will be made, New said. It's also when water supplies are short, so producers should make sure they pump enough water to load the soil profile before then.
Crop water need deficits can range from 6 to 8 inches during that period, leaving the producer dependent on how much rain falls if soil moisture is not adequate, he said.
“You need to determine yield goal and what you are willing to take a risk for rainfall on,” New said. “And you have to get prepared early, especially if you follow wheat with cotton. You have to fill the soil profile deficit.”