Precision ag, cotton PGR 'perfect match'

Well, maybe not heaven, but certainly on high from either aircraft or satellite aerial imagery.

Last year in Mississippi and this year in California, Matt Bethel, a research project manager for NASA at the space agency’s Stennis Space Center near Gulfport, Miss., researched the use of aerial imagery to do a more efficient and economical job of applying the plant growth regulator to cotton.

“This use of aerial imagery in helping to establish variable Pix application rates is an ideal match. Identifying variations of vigor in a field is a straightforward use of imagery. Vigor is what you are looking for in using Pix to slow down growth and improve fruit set,” said Bethel.

Typically, in the emerging world of precision agriculture and aerial imagery is used to detect present or potential stresses to aid consultants and farmers in mitigating the causes, be it insects, lack of nutrients, salinity, water, soil conditions, diseases or other factors.

Last year in the first of three years of researching variable rate Pix on Mississippi cotton, Bethel said plant growth regulator input costs were reduced by almost 25 percent on Kenneth Hood’s farm near Gunnison, Miss.

“The yields were the same between what we call prescription or variable Pix applications and the standard single rate for the entire field,” said Bethel.

And, there is no reason not to expect the same thing from the research work Bethel is conducting at Ted Sheely’s farm near Lemoore, Calif. as part of the Ag 20/20 project NASA is participating in to find practical uses for aerial imagery in agriculture.

“The goal of Ag 20/20 is to find ways to reduce farmer input costs; maximize yields and reduce environmental impact by applying pesticides, herbicides, plant growth regulators or nutrients only where they are needed,” said Bethel.

“The key to what we are doing is putting numbers to everything we do. In Mississippi, David Laughlin, Mississippi State University economist developed the cost savings numbers for the project on Mr. Hood’s farm,” said Bethel. “In Fresno, Michel Pappi, director of the Center for Ag Business at California State University, Fresno, will develop the cost-benefit numbers for the work at Ted’s farm.

“Bottom line is whatever we do in precision agriculture must pay for the farmer. It may sound ground and look great, but if it is not affordable, it will not work,” said Bethel.

His work with mepiquat chloride is straightforward.

Field aerial photographs are taken from an aircraft of fields and vigor areas are identified where a Pix application may be beneficial. A consultant, in this case Nick Groenenberg of Hanford, Calif., Sheely’s independent pest control advisor, uses those maps to plant map areas where Pix may be needed.

“The idea behind using GPS is not to take the consultant out of the field, but make his job more efficient by identifying aerially areas for him to scout,” said Bethel.

“We are mapping with an aircraft flown by OSKI out of Torrance, Calif. using the same aerial imagery system that is available in a satellite. Once the technology is commercialized, it would be available using satellite imagery,” said Bethel.

The research is using three replicated scenarios:

  • A solid one-rate application for an entire field.
  • A off/on scenario where the same rate of Pix would be recommended for various zones in the field with the application equipment turned off an off based on Groenenberg’s recommendations.
  • A truly variable rate technology where five different rates would be used in five difference zones identified throughout the field.

These variable rate scenarios are programmed onto a field map for use in an on-board computer in the ground applicator that automatically adjusts the application rates on the go.

Using a plant growth regulator to control growth and enhance fruit set has become almost standard operating procedure across the U.S. Cotton Belt. However, it use and rates can vary widely each season. Like this year at Sheely’s farm, he was not anticipating high Pix use because fruit retention in the 2002 crop has been very high.

“Insect pressure has been low this year and there has been little fruit loss to lygus. Ted was not going to use much Pix this year, but there were some 105 to 110 degree days this summer where some squares fell off and he decided to use a plant growth regulator to slow down growth and set fruit,” said Bethel. “However, it was a light year for Pix.”

Sheely is a one-shot Pix user while other producers in California and elsewhere use multiple applications.

“In Mississippi at the Hood farm, they may apply Pix three times in a season,” he said.

Pix is applied using recommendations from either seed companies, local universities or what the manufacturer recommends for timing and use rates. “We wanted to base our research on local recommendations and guidelines producers and consultants were comfortable using in making a Pix decision,” he said.

While Pix has become a standard across the U.S. Cotton Belt, there are some striking differences in cotton cultures between the Mid-South and California.

“The most striking difference…other than the humidity,” said the Mississippi based Bethel, “is how labor intensive farming is in California. There are always workers in the fields in California…weeding and irrigating. The only thing you ever see in a field in Mississippi is a tractor,” said Bethel.

In California, irrigation is “so critical,” Bethel said. Irrigation is supplemental in Mississippi.

“There is a very narrow window for a Pix application in California because of the need open and close irrigation ditches and get in and get out before the next irrigation cycle,” he said.

“Getting this variable rate technology in an aerial applicator will make a big difference in California in getting farmers to accept the idea of prescription Pix applications,” he added.

While the Pix application window can be narrow, the California growing season is longer. “You don’t necessarily have to rush things in California…to get in a big hurry to get open bolls out of the field,” he added.

California definitely has the advantage when it comes to aerial imagery.

“You don’t have to worry about clouds in California in the summer. You want it to be clear for a satellite to take photographs. You can count on that in California, but not Mississippi,” said Bethel.

What is common between the two areas is soil type variability within fields. “What you don’ t see in Mississippi and what has a big influence in California is salinity, which is the biggest factor Ted has to deal with in field variability,” he said.

Regardless of those differences, Bethel is confident, based on what he has seen in both regions, that precision agriculture prescription applications of Pix will work to save growers money in both places.

e-mail: [email protected]

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