Arkansas Rice: Harvest Remains Slow but Yields “Solid;” Soybean Desiccant Drift

Harvest progress still remains slow at this point without much to update.  Still calling yield reports “solid” so far with most seeming satisfied and only a couple of disappointments.  More rice is very close to being ready, but the slight drop in temperatures and increase in clouds hasn’t given us the grain moisture drop we need to finish maturing.  The couple of days of lower humidity this week didn’t deliver the heat and sun needed to go with it.

A number of comments this week of samples being taken thinking rice looked ready only for it to still be 23-25% moisture.  The reality is that when conditions turn favorable, moisture can drop a few points in just a few days, but it can easily take a week to drop a few points if drying conditions aren’t good.

The forecast for next week seems to get modified by the minute.  While the overall rain chances look very low, every day is forecast to have very high humidity (100% overnight!), be partly cloudy, and 30-50% chances of rain.  As Harry Hogge in Days of Thunder said, “this is not the kind of answer I’m looking for from you.”

Let us know if we can help.

Fig. 1.  NOAA 7-day precipitation forecast. Click Image to Enlarge

Preliminary Planting Date Yield Data

Table 1 contains preliminary yield data from 2022 and 2021 planting date studies at the RREC at Stuttgart.  Reminder: the 2022 data is preliminary because we haven’t fully analyzed it yet – so it may look different in its final form presented later this year.  Since we start getting questions about performance data already, we’re showing this now for an ‘early look’.  Also note these were all managed with a conventional herbicide program so that everything could be included in one trial.

Table 1.  Preliminary planting date study date for 2022 versus 2021 data.

Grain Type: L = long-grain; M = medium-grain; CL = Clearfield long-grain; CM = Clearfield medium-grain; FL = FullPage long-grain; ML = MaxAce long-grain; PL = Provisia long-grain; LA = long-grain aromatic.

Soybean desiccant drift on late season rice

Some phone calls have started coming in asking about the impacts that soybean desiccant [Gramoxone (paraquat), Sharpen (saflufenacil), and salt (sodium chlorate)] drift will have on late season rice.  In addition, further questions have arisen about the impacts of potential drift of late season soybean herbicide applications to control grass escapes (glyphosate and clethodim) will have on rice at this stage.

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First and foremost, our goal should be to NOT drift onto neighboring crops regardless of the potential or lack thereof for injury.  Herbicides, particularly systemic ones, can do some very crazy things from time to time when plants are in reproductive stages.  Minimizing the likelihood for drift (proper sprayer setup, waiting for the right wind direction, etc.) will help to mitigate potential problems such as yield loss or reductions in quality that can cause dockages or outright buying point refusals.

In the event that drift does occur onto our rice at this stage from a late season soybean application to control grasses or desiccate the crop, there’s a couple of things to watch out for.  First, minimal to no visual injury symptoms are typically observed from drift rates of herbicides when rice is in the reproductive stages.  The results of the drift incident will only be evident once the combine rolls through the field.

When it comes to yield loss, recent research out of Mississippi has shown that simulated drift rates of Gramoxone (paraquat) can cause some fairly significant yield losses and reductions in grain fill due to drift occurring anywhere from 50% heading (16-19% loss) up until one week prior to harvest (5% loss).  Additionally, seed weight (grain fill) was reduced for all application timings of simulated paraquat drift except for one week prior to harvest.

Simulated drift rates of glyphosate caused reductions in yield (6-19% loss depending on timing), but no losses in grain fill occurred at any point from 50% heading to one week prior to harvest.  In contrast, simulated drift rates of Sharpen (saflufenacil) and salt had no effect on rice yield or grain fill.  Additional research suggested that inbred cultivars tended to be more sensitive or result in more yield loss from late season drift events of desiccant herbicides.

As we’re nearing the end of the season, and we see the light at the end of the tunnel, let’s make sure to take care to avoid these drift situations and allow everyone to finish off on a positive note. Good luck out there!

Fig. 2.  Example of paraquat drift onto early season rice to show symptomology (later season drift may differ in appearance). Click Image to Enlarge