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With VR sprays: Poor-yielding parts of field improve

Editor's note: This is the third installment in a series of articles on Glendora, Miss., cotton producer Ricky Belk's experience with variable-rate applications of plant growth regulator, insecticide and defoliant during the 2005 season. Belk is trying the technology on a 750-acre farm with highly variable soils. Precision agriculture technology provider InTime, Inc., Cleveland Miss., is an important part of the program, providing Belk with aerial images of the farm, which can be converted to several uses for variable-rate applications.

When Glendora, Miss., cotton producer Ricky Belk wanted to evaluate a variable-rate application of plant growth regulator on a 750-acre farm this fall, he knew exactly where to go — to where the farm traditionally produced the shortest plants.

He figured it was there that the variable-rate application would do the most good. He explained that with a single-rate or blanket application of plant growth regulator on the entire field “we had some (weak) areas where we always over-applied plant growth regulator because the rate was based on the good spots.”

So with the shorter plants receiving less plant growth regulator or none at all, Belk figured he could save money and do a better job of managing that particular stalk size.

Belk liked what he saw when he got to the weak places. “The bad spots are so much more comparable to the good spots now. This field was probably the most un-uniform field that I have. This year, it is as uniform as any field that I have. We helped the bad spots more than we helped the good spots.”

The farm was a perfect example of how fields with a lot of yield variability can benefit from variable-rate applications.

In July, Belk ordered an aerial image of the farm from InTime. The image was used to develop a scout map, which shows how plant biomass is distributed in a growing cotton field. Biomass is directly related to plant vigor.

The scout map has seven management zones, ranging from high biomass to low biomass. Belk's scout, Billy Bryant, went into the farm's fields and checked the crop condition in each of the zones, and he and Belk developed a variable-rate prescription based on them.

Guided to problems

Belk likes the idea that Bryant is spending less time tracking down problem areas with the help of InTime imagery. “To me, the more time that Billy has to spend in problem areas, the better job he can do for me. There may be some farmers who want their consultants to spend all day on their farm, to make sure they get their money's worth. But I want my money's worth where it needs to be spent.”

This season, they used three InTime images to guide them in making variable-rate applications of plant growth regulator, and defoliant and one application of insecticide for plant bugs.

The variable-rate insecticide application was not a planned spray, but Belk and Bryant saw the opportunity and decided to give it a try. “We saved a good bit of money on the insecticide and got control of the pest,” Belk said. The producer was also looking to save money on a variable-rate application directed at spider mites, which have a tendency to infest fields in hot spots. “They were right at threshold, then we got the right weather, they disappeared and we didn't have to spray.”

One of Belk's original goals was to not scrap as much cotton, which could be a benefit of a more uniform crop. But weather threw a monkey wrench into those plans. “This cotton actually needed defoliating two weeks before I pulled the trigger. Hurricane Katrina was coming through, so I held off. I wanted as many leaves as I could get on the plant for protection.”

After he dodged that bullet, Hurricane Rita blew into the Mid-South, delaying defoliation again, and putting him further behind.


Belk went with a one-step, variable-rate defoliation, then went back with an airplane to touch up some spots. “If we had defoliated the cotton when it was ready, we wouldn't have had to do the touch-up work.”

While the crop is definitely more uniform because of variable-rate applications, Belk had not ruled out that some scrapping may occur.

Variable-rate applications are also having a positive impact on productivity, increases. “The average gallonage per acre was 7 gallons instead of 15 gallons, so we were doing fewer loads for the entire farm.”

Belk says he is just beginning to understand the potential for additional uses of variable-rate technology. For example, when the skips in Belk's 2-1, skip-row cotton get a little grassy in the future, he would like to make variable-rate applications of Select. “I believe an image could have shown exactly where the grass was and we could have put that into the applicator and sprayed it. Once you start thinking about it, there are a lot of possibilities.”

While precision agriculture is sometimes difficult to evaluate through scientific methods, Belk knows it's working. “I think we have an increase in yield over what we would have had, had we not used variable-rate. We used to have little bumblebee cotton in the bad spots. We have cotton waist-high there now.

“It's way more than paid for itself,” Belk said. “Going into next year, I'll know a little bit more about it. It's like going to Roundup Ready cotton. You have to learn how to use it.”

Belk will enroll the 750-acre cotton farm in InTime's variable-rate program again next year, and wants to add dry, variable-rate applications to the program, now that the application technology is available. “It's a whole other area to look into.”

According Alan Whitman, sales representative for InTime, the technology can help Belk apply both pre-plant and side-dress variable-rate applications. “With fertilizer prices where they are, there is a tremendous opportunity to save money by putting it exactly where it's needed.”

Input savings

That could also translate to less plant growth regulator and defoliant being applied to areas that may have received too much nitrogen. “It won't always work exactly like that because your stronger ground is still going to be stronger than your weaker ground,” Whitman said.


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