What is in this article?:
• As irrigated cotton acres continue to increase in the Southeast, growers are looking for the most efficient method of watering their crop, and they want to know how the cost of drip irrigation compares to the tried-and-true center pivot system.
COTTON PRODUCERS IN the Southeast are exploring subsurface drip irrigation as a viable option for watering their crops more efficiently.
GPS system a must
“What are the implications of the depth of your drip tape in terms of tillage? For certain, you have to be committed to a GPS auto-steer system and reduced tillage to insure that you don’t rip up the tape,” he says.
From an economic perspective, says Shurley, common sense would tell you that drip irrigation fits best in small, irregular fields where you can’t place a pivot.
“Rather than having a pivot, since you can’t go a full circle, maybe you could use drip there.
There also are non-irrigated fields that are irregularly shaped. If you put out a pivot, there will be areas of the field that remain without water. Maybe drip could be used in those areas with a pivot. It sounds simple enough, but it’s not.”
The UGA research began two years ago, but Shurley’s results are from 2011 because that was the first full year of drip trials.
“We’ve have 16 treatments that are subsurface drip at two depths — shallow and deep — planting two varieties. We had four different ways of determining when to water, how much to apply, and how much water to apply once it was triggered. Each treatment was replicated six times. With our center pivot comparison, we had two varieties and two application amounts and four treatments.”
The irrigation applications were made according to the University of Georgia checkbook method which tells you how much water is needed at certain physiological stages of the cotton plant on a weekly basis. It tells how much water is needed up through seven weeks after bloom.
“Average yields from one year of all applications show no difference in the treatments between center pivot irrigation and drip, says Shurley.
“It shows that drip can get the water out there and keep yields at the same or near the same as with a center pivot. That’s good in terms of the confidence factor.
“The other thing we saw, and it was not significantly different, was that the drip tape set at a shallow level tended to yield more than the deep-set tape, but it’s not a statistical difference.”
There are several economic conclusions that can be drawn from this one year of research, says Shurley.
“No. 1, drip can yield as well as center-pivot irrigation. Secondly, the shallow yields tended to be higher than the deep, but they were not statistically different.
“Another important factor is that drip can possibly yield as well as center pivot, but with less water. Because if the checkbook method calls for an inch of water, and you put 1 inch out there, the crop isn’t getting all of that water. Center-pivot irrigation only has 60-percent application efficiency.
“If the recommendation calls for an inch, maybe you should be putting out 1.5 inches.”
With drip, says Shurley, you can put out water slowly over the course of a day, and if you put out an inch, you can be pretty sure that 1 inch will get to the plant.