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08
May
2016
When Rice is Ready to Flood, but Field and Levees Aren’t
Author: Jarrod Hardke, Rice Extension Agronomist

The heavy rains that hit the state a week ago have left many well prepared fields in rough shape. Washed out levee gates and blown levees are all too common.

For many of these fields there’s plenty of time to get things patched up. But for some out there, the rice is reaching time to flood and that’s just not an option with the field situation. So what should we do?

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I strongly recommend you run a DD50 report (http://dd50.uaex.edu) for a little guidance on application timings – based on research for specific cultivars.

Basically if you’re just getting to 4 leaf rice you have about 2 weeks until you hit the end of the recommended window for preflood nitrogen (N) application. Those in this situation have asked “should I go ahead and apply 100 lbs of urea or some ammonium sulfate ahead of these rains?” No, you shouldn’t – you have time, don’t go to Plan B before you’re done with Plan A. Again, you have time to wait to flood if you leave the rice alone, but as soon as you give it a kick with N that window closes fast and you increase the likelihood that you’ll have to keep putting out N that way.

In addition, every application made that is not well incorporated by a permanent flood is subject to major N losses. Since those losses are highly variable it makes N management very difficult for the rest of the season. When we’re forced to start guessing at N rates based on N loss it gets difficult to supply adequate N without going overboard and causing other problems.

On the other side, if we reach the end of the N application window and we still haven’t been able to get the field ready to flood, the game changes. At this point the plant needs to be supplied with some N. So 100 lbs of urea or ammonium sulfate ahead of a rain would work. From there it becomes a simple choice each week, either the field is ready to flood or more N needs to be applied. To fertilize rice all the way out like this will probably take at least 4 shots of urea at 100 lbs each. At least. Not cheap. Let’s hope that’s not the hand we’re dealt.

In situations other than normally applying N and flooding, you should always use small application rates such as 100 lbs of urea. Applying large amounts of N to young rice without incorporation by a deep flood leads to loss of most of the N before the plant ever has a chance to take it up.

So in review:
1. Run a DD50 report! (http://dd50.uaex.edu)
2. Wait until the end of the Preflood N window (Final Recommended Time to Apply Preflood N in DD50) for dry soil conditions & field ready to flood before applying any N.
3. At the end of the window, if still not ready to flood, begin spoonfeeding small N amounts ahead of rain to incorporate.
4. Continue applications weekly until field can be flooded – apply remaining N needed including offset for losses in previous applications and flood up.

Contact us if you have questions about specific situations.


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