STUTTGART, Ark. — Pre-flood nitrogen efficiency is always a topic of concern for rice growers because so much is invested in this input. Nitrogen fertilizer typically costs rice farmers as much as $50 per acre, including application, and may be even higher for some situations.
Also, the preflood nitrogen is critical because this application determines the yield potential for the crop. Midseason nitrogen simply maintains yield potential already established by the preflood application.
To get the maximum efficiency, the Arkansas Extension recommendation has been to apply urea onto dry soil and flood up as quickly as possible, preferably within three days.
However, the number of fields that can be flooded this quickly is small, with many fields typically requiring 10 to 14 days to flood up.
A new product, known by the trade name Agrotain, may have some promise for farmers who have limited water and need more time to flood their rice. Agrotain is a urea-nitrogen fertilizer stabilizer that reduces loss of nitrogen that normally occurs when urea is surface-applied and not quickly incorporated.
Questions about Agrotain performance for rice have been extensive during the last two to three months and during the 2002 growing season.
Several producers who attended our production meetings indicated interest in using Agrotain nitrogen stabilizer for rice this year.
The purpose in discussing Agrotain at the meetings was to keep everyone updated on the latest research information and to respond to questions generated during the 2002 growing season, for which Extension had no data to support.
I now have one year's worth of data, which is not enough to strongly recommend the product for 2003. Studies conducted by Rick Norman, Nathan Slaton, and me, however, are positive.
Although it looks like an effective product, we have only one year of complete data where nitrogen loss and grain yields were recorded.
The product also looked promising in field-size demonstrations conducted during 2002 in Arkansas. Extension specialists are testing the product again this year, but what works one year may not work the next.
It looks promising but we have all seen things look good one year but not work in the end. I would encourage you to let us research it further before using it on a large acreage.
Studies conducted on clay soils suggest that loss of nitrogen from urea applied on these soils is not as great as on silt loam soils. Only about 5 to 10 percent loss was measured even when the flood was delayed for 10 days after application. As a result, clay soils may not benefit as much from the use of Agrotain as silt loam soils.
The major advantage of Agrotain, compared to other improved nitrogen sources, is the cost. Although other products have been developed that are as good as or superior to urea, they have typically been cost prohibitive. In contrast, the cost of Agrotain is at least low enough to be competitive.
This has certainly generated a lot talk among growers. If Agrotain is used and decreases nitrogen loss by 10 to 15 percent, that could be a significant amount of additional nitrogen for the plants, which may affect midseason nitrogen application decisions. However, improved efficiency of the preflood application should result in better yields.
Charles E. Wilson Jr. is the Extension rice agronomist at the University of Arkansas Rice Research and Extension Center in Stuttgart. e-mail [email protected]