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Nutrient decisions made easier

Technology may one day make it easier for cotton growers to determine plant nutrient levels and apply precisely the amount of fertilizer the crop needs to grow most efficiently.

“New techniques are on the horizon that we think will improve the grower's ability to monitor nutrient levels in cotton,” Morteza Mozaffari said during a tour of research plots at the 75th anniversary field day of the Cotton Branch Experiment Station at Marianna, Ark.

One method, he said, analyzes light reflected from the crop canopy to measure nitrogen levels and determine if a deficiency exists. The spectral radiometry method involves driving a camera over the top of the canopy to analyze light reflectance; those data are then used to make nutrient recommendations.

Another method, uses remote sensing and aerial photos to determine existing nutrient levels. Data are fed into a computer, which then tailors applications to meet the plants' needs.

“We feel this is promising technology,” Mozaffari said. “We hope it will lead to a nutrient analysis method that will eliminate the need to go through the fields and sample or take readings.”

Presently, he noted, many growers rely on petiole analysis to determine how their crop is faring from a nutrition standpoint.

“Cotton needs very intensive management of nitrogen during the growing season. In Arkansas, we're fortunate to have a lot of research that makes it possible for growers to sample their crops, send petioles to the lab, and get information that helps them make decisions regarding fertilization.”

New cotton varieties in recent years have necessitated a re-evaluation of fertility programs, Mozaffari said.

“As more growers have moved to shorter-season varieties, there has been a need to re-examine fertility programs to help insure that producers can get the most from their fertilizer money, while attaining optimum yield.”

Studies are also being done at the Marianna station to analyze the impact of land leveling on crop yield.

“Leveling is becoming increasingly popular, because it allows growers to more efficiently manage irrigation and drainage,” Mozaffari said. “At the same time, many producers have found that crops planted on leveled land don't produce a uniform yield. In fact, it's common to see spots in a newly leveled field that have poor yield.”

A better understanding of how soil properties change during typical land leveling may help growers better manage soil fertility, improve crop uniformity, and obtain higher yields, he said.

“In general, we've found that land leveling has reduced soil pH in several spots, coinciding with areas where soil was removed. Limestone applications were necessary to produce a healthy crop.”

Leveling also increased the amount of potash fertilizer needed for optimum yield, Mozaffari said.

“These variabilities can be shown by grid-sampling the field. The grower can use these data to develop maps for variable rate lime and fertilizer applications.”

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