Arkansas Rice: Hurricane, Cool Temps – This Crop Needs A Break

Mature rice flattened by wind. ©Debra L Ferguson

The expected rains this week were even more prevalent than expected following Hurricane Laura. Some areas have now seen rainfall for 6 to 7 consecutive days. Areas that experienced initial lodging from Laura have worsened and will likely continue to do so, but some have held firm.

From here, the game is getting into the field as quickly as possible, with the need to see some sunshine over the weekend. Next week will begin a hard run at harvest as we have lost more than week of harvest progress on our earliest rice that is ready to be cut.

The falling temperatures and humidity next week should aid in rapidly drying the crop – but we will need to work quickly as any rains that return after rice has dried rapidly will have the potential to re-wet the grain and cause fissuring, which can lower head rice yields.

Spotty harvest attempts have occurred this week around rainfall events, and more will try to make progress where possible over the weekend. But many areas still need a couple more days before they can even get turn rows dried out enough to get in and out of fields.

Cool Temps On Late Rice – Possible Outcomes

There is enough June planted rice to be concerned about the upcoming forecast. Over the weekend, highs are to remain in the 80s but lows will be around 60 and below depending on the south versus the north end of the state.

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Even more concerning are the temperatures into next week when we are expected to see highs in the 70s and lows around 60 in the south and mid-50s in the north.

If rice is around panicle initiation (PI) [doesn’t really apply to us right now], then temperatures down close to 60 and below can cause yield loss by reducing the number of kernels and branches formed in the panicle. The recommendation would be to increase flood depth to buffer the temperature drop and protect the growing point, which would be near the ground.

If you have rice that is 7 to 10 days before heading, then temperatures this cool can disrupt pollen formation and lead to spikelet sterility as a result. Increasing flood depth may help buffer the micro- climate in the field, but probably not well as the flood only buffers the temperature 4 to 6 inches above the water line. Very few fields are likely in this position.

Fields flowering during this cool period may see a lack of pollination of kernels due to decreased humidity. About all we can do is hope that flowering dodges the worst of the temperatures.

For rice past flowering but in the grain filling stages, there is little direct risk of negative impact. However, plant progress will slow (almost appear to stop). However long cool temps last, it will likely take twice as long to see noticeable plant progress again.

So, our biggest concern is overall delay in crop maturity, which will delay harvest and potentially reduce grain weight as a result.

Overall, there is little we can do but hope that temperatures are not as cool as forecasts predict and that we get lucky on the timing of the cool spell relative to our rice growth stage. Keeping the flood depth up (shouldn’t be an issue with all the rain) and delaying draining of fields still ripening, may help limit the impact but not likely.

Wind Damage: Mixed Outcomes

While lodging wasn’t as great as feared, later rice may have been affected to a larger extent than originally thought. A significant amount of wind damage is appearing now in later rice. Some are confusing it with bacterial panicle blight.

It’s not impossible for bacterial panicle blight to develop, but most everything we’ve checked out so far is from physical damage due to high winds.

Rice growth stage is the most important factor in this happening. Rice kernels that are around the flowering stage are most susceptible. Wind speeds don’t actually have to be all that high to cause this type of injury. Certainly, the higher the wind speed the greater the chance it happens.

Heavy rainfall alone can cause similar injury to the delicate flowering parts of the plant. When rainfall comes in with increasing windspeeds then you have a recipe for major impact.

However, examples of needing to catch rice at just the right time were very evident this week. Research trials in different counties that experienced different weather from Hurricane Laura told that story.

KIn Phillips County, lodging was minimal due to lower winds and rainfall, but blanking was much more severe than in a similar trial in Arkansas County where greater winds and rainfall were experienced and rice lodging in the area was worse. The difference in maturity of the rice between these two trials was very slight.

As rice passes the flowering stage and enters milk stage and beyond, it takes much more wind and rain to cause enough physical damage to impact kernel development.




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