Nitrogen fertilizer study providing answers

Frances Gould, Schultz, Bruce  |  1/24/2017 8:24:29 PM

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An airplane applies fertilizer immediately after a field is harvested on the Fontenot Farm in Evangeline Parish, and a mower is used to cut the rice stubble to increase second-crop yield. AgCenter studies have shown the benefits of mowing or rolling stubble after harvest to improve yields, and now work is being done on the use of gibberellic acid to further increase second-crop yields. Photo by Bruce Schultz

AgCenter rice agronomist and rice extension specialist Dustin Harrell looks over research plots testing the seeding rate for different varieties. Photo by Bruce Schultz

LSU AgCenter agronomist Dustin Harrell has been studying nitrogen and seeding rates for potential Clearfield and Provisia varieties.

“The objective is to have an agronomic package to coincide with the release of new varieties so we can answer questions about how they are going to respond to nitrogen fertilizer and the proper seeding rate,” Harrell said.

The nitrogen fertilizer study is being done to learn how much a variety can be pushed with fertilizer before lodging and excessive disease occur.

The work is not limited to releases by the AgCenter. Harrell is looking at seeding and nitrogen rates for varieties released by Mississippi State University and the University of Arkansas as well as RiceTec.

Research trials in 2016 were conducted on more than 5,100 plots at seven locations statewide.

“We also continue to evaluate urea and fertilizer treatments designed to reduce volatility,” Harrell said. “There may be new products in the future.”

“Although current nitrogen fertilizer efficiency is good in rice production when best management practices are used, we can always do better,” he said.

The stubble management study on ratoon rice could not be completed in 2016 because of wet weather and flooding at harvest of the first crop.

But Harrell said his 2016 work on the use of gibberellic acid (GA) to increase ratoon yields was completed. In 2015, data showed an increase of 3 barrels (10.5 bushels) when the material was used at the rate of 4 ounces an acre with stubble management. Even in rice with no stubble management, 4 ounces of GA boosted yield by 2.2 barrels (7.8 bushels).

Ratoon test plots harvested in 2016 showed rice sprayed with GA had a yield increase, but it was not as significant as the 2015 test results.

Texas rice farmers have used the chemical with good results. “We want to have three years of data before it is a recommended practice by the LSU AgCenter,” Harrell said.

The GA application has to be made when the grain is in the soft dough stage of the first crop, otherwise the chemical stimulates growth at the wrong time and could cause a plant to grow taller and increase the chances of lodging, he said.

The application could be tank-mixed with a pyrethroid sprayed for stinkbugs on the first crop, he said.

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