Arkansas Rice: It’s a Jungle Out There, and There Are No Easy Answers

Crop Progress

“It’s a jungle out there, kiddies.  Have a very fruitful day.”  The rice and the weeds are both growing rapidly under the hot, sunny conditions.  Many growers are reporting having to work with an alternate wetting and drying type of flood just trying to keep up.

Not to be all negative, but some helpful rains are likely needed soon across much of the region or irrigation decisions are looming.  Nobody wants to have to choose between keeping rice flooded and watering soybeans, but it may come to that if this weather pattern doesn’t change.

I stumbled across Fig. 1 on social media and thought it was appropriate for a lot of the questions coming in these days for dealing with difficult field situations.  Most answers require long conversations, not quick recommendations.  The hope is for simple, but lately complex has been more common.

Just how much heat have we been accumulating?  Fig. 2 shows the DD50 unit accumulations since May 1 for 2010-2018.  May 1 was chosen since that’s around when a large percentage of the acres were considered emerged.  Put simply, 2018 has given us more DD50 units in this 46 day period than any year included, ahead of even 2010 and 2012.  What happens between now and August will tell the tale.

Fig. 1. You want answers?

Fig. 2. DD50 Unit Accumulation by Year, May 1 – June 15. Click Image to Enlarge

Midseason Nitrogen Application Timing

With much of the rice in the state reaching panicle initiation (green ring) or beyond, it’s time to review best management of midseason nitrogen application.  Remember, these comments refer to varieties, not hybrids.

Before applying midseason N, rice should at least be at green ring AND it should be at least 3 weeks (21 days) since the preflood N was incorporated by the flood.  Applications made before reaching both of these minimums may have reduced benefit, as the rice is not finished taking up preflood N.

Fig. 3 shows that it takes over 21 days after preflood N application to consistently receive the maximum benefit from a midseason N application.  The window from there is approximately 3 weeks long to get the same maximum benefit.  So we do not have to rush, we have a workable window to get the application out right.

Fig. 4 provides a different way of looking at the same data.  Working strictly off of application timing we see that we consistently get the greatest benefit from midseason N applications between green ring (0) and 21 days after green ring.  After that, the benefit begins to decline.  This data has been compiled from 2012-2017 using different varieties including Diamond, CL153, Roy J, CL152, Taggart, Mermentau, and Cheniere.

Issues with preflood N applications and early deficiency symptoms may require a change from the standard recommendation.

Before applying midseason N to rice, BOTH of these conditions must be met:

  1. 3 weeks since preflood N was incorporated with the flood, AND
  2. Rice must be past green ring.

Fig. 3. Yield response to midseason N timing by days after preflood N. Click Image to Enlarge

Fig. 4. Yield response to midseason N timing by days after green ring. Click Image to Enlarge

Loyant Injury to Rice

Last week there was a picture of some injury to rice that was listed as glyphosate drift.  There were certainly indicators in the field for that, but further inspection and additional field visits show it to be injury from Loyant (Fig. 5).  From our tolerance trials we do know that there can be some injury from Loyant and extremely hot conditions could help induce it.  The “bunched” leaf inside the stem here seems more physical related to leaf collar constriction slowing the leaf’s emergence from the sheath.  It should come out and be fine.

Keep in mind that it is stated on the label that field ends and edges should not be “dressed” (that is, overlapped our double sprayed).  Excessive rates and tank mixes may compound potential injury, which can take up to 14 days before noticeable.  Hybrid rice and medium grain varieties can be more sensitive than pure-line long-grain varieties.

Fig. 5. Loyant injury to hybrid rice.

LockDown Herbicide for Northern Jointvetch Available in July

The biological herbicide LockDown will be available beginning the first week of July for those concerns about Northern jointvetch management.  We’re including this notification because supply will be limited and can direct you to the appropriate contact person if needed.

Rice Field Day Scheduled for Friday, August 3

The Rice Field Day at the UofA Division of Agriculture Rice Research & Extension Center is scheduled for Friday, August 3, 2018.  More details will follow.

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