Scattered rainfall across the state this week certainly has things looking up. Not for everyone though as rain totals ranged from only a few tenths to a few inches. Even the small rainfall amounts created a noticeable improvement in overall rice appearance in the state.
The rice crop is actually in very good shape at the moment, difficulties with the dry weather aside. Planting progress is extremely close to wrapping up (Fig. 1) and the combination of flushing and a little bit of rainfall has created a tremendous jump in crop emergence (Fig. 2).
If you’re paying attention to your DD50 reports you should be re-running those reports right now as we have accumulated many more heat units than the 30-year average recently. For example, for rice emerged April 29 a report run on 5/5 versus run again on 5/15 saw dates move up by 3 days. That is, instead of the optimum preflood window beginning 5/16 it’s now 5/13.
It’s very easy to get behind under these conditions, and timely preflood N management is critical to maximizing yield. Be prepared to act on the early side and remember that while rice height matters regarding flood depth – actual rice growth stage is most critical for timing management.
Scout for Rice Water Weevil Injury as Fields are Flooded
A quick look at rice fields that have been flushed lately has shown some intense rice water weevil (RWW) leaf scarring (Fig. 3). The hot conditions have insects on the move and this particular insect is drawn to open water in rice fields.
AgFax Weed Solutions
CruiserMaxx and NipsIt seed treatments provide good protection from grape colaspis and RWW injury when we’re able to get rice to flood in a timely manner. However, this year we have a good deal of early planted rice that will have been in the ground for nearly 60 days by the time we go to flood. In this situation the seed treatments have begun to lose their gas.
CruiserMaxx and NipsIt are known to suppress leaf scarring from RWW adults in addition to providing protection from larvae feeding on roots. As you establish the permanent flood, scout for leaf scarring and consult the treatment threshold in the MP144 (here).
Insecticide applications targeting adults RWW need to be made within 10 days of establishing the permanent flood to be effective. Get out there and scout in the days immediately following flood to be sure any insecticide applications needed go out on time. Any acres treated with Dermacor may have scarring but likely will not require treatment as this seed treatment persists longer.
Keep Your Head On a Swivel, Flood Time is Near!
We’re having a heat wave, a tropical heat wave. With temperatures soaring rice has caught the fast train to flood time – especially if you’ve given it a recent flush to combat dry soil conditions. It’s time to touch on a few tips for getting rice to flood with maximum nitrogen uptake.
Dry soil conditions are currently the easiest thing to find out there. However, keep in mind that as long as some of these fields have been without a rain, it’s going to take longer to establish a permanent flood due to a lack of moisture in the soil profile. What does that mean? If you’re not careful, you could experience greater nitrogen loss than usual due to flood-up taking longer.
Multiple-inlet rice irrigation (MIRI) is always a good idea, but under dry conditions like these, it can drastically reduce the time needed to establish a shallow flood over the entire field to 1) maximize N efficiency and 2) reduce weed control costs.
If you’re flooding up and it’s still extremely dry:
- Use MIRI to flood up all bays equally and quickly.
- Use urea treated with a recommended NBPT product to minimize volatilization losses which occur when urea is left on the soil surface unincorporated by flood.
- If extremely long times to flood establishment are expected, consider increased the N rate slightly, particularly on areas of the field which will take the longest to establish the flood.
If you’re flooding and rains mess up the plans:
- Run a DD50 report to establish your optimum N window and final N date.
- Make every attempt to apply N to dry soil before the final N date.
- If soil conditions are still wet at the final date, apply N with an NBPT product to wet soil and attempt to let the soil dry underneath before flooding – but if additional rain occurs start the well.
- If muddy soil conditions persist with more rainfall on the way, apply preflood N and increase the rate by 20-30 lb N/acre and begin flooding.
- If conditions create standing water through the final date, begin applying N in a “spoon-feed” manner – 100 lbs of urea/acre once a week for 3-4 weeks. A minimum of 4 applications is needed to maximize yield for varieties on silt loam soils. More work is needed but it’s expected that one less application may be needed for hybrids in this situation. Use Greenseeker to determine if an additional application is needed.
Managing N in a furrow-irrigated system:
Some type of N split is the best way to go to maximize yields and minimize risk.
- 50% normal preflood N rate followed by 50% normal preflood N rate 10-14 days later. Also apply an extra 100 lbs urea to upper portion of field that dries more severely 7 days later.
- 100 lbs urea once a week for 4 weeks has also been a proven winner in this situation.
- Some have had success with a single preflood application with little to no additional N beyond normal compared to a flooded situation. This is extremely situational and should not be attempted in fields that do not have high native soil N. Generally recommended to avoid, or to at least still apply an additional 100 lbs urea to upper end of field to offset N losses in that area.