It could be called a tale of two seasons: Rice farmers have two distinctive periods for fertilizing their crops – pre-flood and post-flood.

Managing nitrogen applications for those two seasons and following the 4R Nutrient Stewardship Concept are key ingredients in improving rice yields, according to researchers at the LSU AgCenter Rice Research Station.

LSU scientists have been studying rice fertility at the station for most of its 102-year history. Their recommendations for applying nitrogen and other crop nutrients have played a major role in nearly continuous improvement in rice yields over the decades since.

The current crop of researchers, led by Dr. Dustin Harrell, assistant professor of agronomy with the AgCenter, says fertilizing rice in environments that are alternately dry and wet is not the easiest task.

“The complex chemistry associated with the alternating dry and flooded conditions in rice can create an environment for enhanced fertilizer nutrient use when correct management procedures are used,” says Harrell. “On the other hand, a profound inefficiency could result from improper fertilizer practices.”

Production aid

Harrell, a speaker at this year’s Rice Research Station Field Day, says the 4R Nutrient Stewardship program, a concept developed by the International Plant Nutrition Institute to help improve nitrogen application efficiency, could be beneficial to Louisiana producers.

“The right source, right rate, right time and the right place are the components which make up the 4R Nutrient Stewardship concept,” says Harrell. “The 4Rs can be used to help make informed and practical site-specific, sustainable fertility decisions in rice production.”

Because the right nitrogen fertilizer source is critical in rice production, Harrell says fertilizers that contain a portion of N in the nitrate form, such as ammonium nitrate, should be avoided.

“Rice fields remain flooded for extended periods of time during the season, creating an anaerobic soil condition,” he notes. “Under anaerobic conditions, nitrate-N can be transformed to gaseous forms and be lost to the atmosphere through denitrification.

“However, ammonium-N will remain in stable in the ammonium form under these same flooded, anaerobic conditions if applied properly. Therefore, only ammonium and ammonium-forming fertilizers should be applied.”