Arkansas Rice Update 6-9-23

by Jarrod Hardke, Rice Extension Agronomist - June 9, 2023

Arkansas Rice Update 2023-12

June 9, 2023

Jarrod Hardke and Trent Roberts

“There’s something happening here, but what it is ain’t exactly clear.”

Gimme a Break

Just as it was starting to feel like summer, conditions are backing off for the next several days.  While last weekend’s rain chances didn’t really produce much, throughout this week scattered showers have delivered varying but mostly small amounts to localized areas.

Now this weekend through next week is starting to look like most of the state could receive a couple inches of rain.  These look to be spread out in smaller events, but the milder conditions should make small rains more impactful.

Prolonged dry conditions have made weed control a tall order going to flood.  While the majority of acres have now been flooded, we’re still battling on the remaining acre and some rice just got planted.  Fields that had multiple applications of overlapping residuals early appear to be the cleanest.  The best weed control is never letting them come up in the first place.

But depending on planting date that wasn’t always possible – because you need rainfall for residual activation.  As a result there are fields where it’s too dry for any herbicide to work well on emerged grasses, meaning we need to do what we can and get the rice to flood.  Focus on cleanup shots shortly after flooding – the grass may be a little larger but the moisture will be there for better herbicide activity.

We’ll go more in-depth on midseason nitrogen (N) timing next week, but remember that for pureline varieties we recommend waiting until at least 4 weeks after the preflood N is incorporated before applying midseason N.  This gives us the best chance to maximize our response to midseason N.

Let us know if we can help.

Fig. 1.  NOAA 7-day precipitation forecast.

Depth of Incorporation

Jarrod Hardke

“We didn’t do anything different with our herbicide rates and programs, but we’ve got injury.  What gives?”  If I had a nickel for every time I’ve heard a comment like that over the last few weeks, I’d have a lot of nickels…

The hot droughty weather over the past month has had rice and weeds in a regular state of stress.  One major player in that has been a never-ending north wind (which seems to finally be changing with the incoming front).

Ultimately, the dry soil profile may have a lot to do with odd herbicide responses this spring.  Quinclorac (e.g., Facet) and ALS herbicides (e.g., Permit) have routinely caused injury that we generally associate with spring weather that is cool, cloudy, and wet.

One theory is that the dry upper soil profile is causing incorporation of these herbicides to a greater depth into the root zone than usual when we’ve been putting fields to flood of late.  In most instances, simply allowing the flood to naturally fall back has readily enabled plants to recover from the herbicide stress.  Only in rare cases has injury been severe enough in areas of fields to warrant actually draining and attempting to dry the soil to prevent plant death.

Fig. 2.  Quinclorac herbicide injury to rice.

Using Tissue Sampling Effectively

Trent Roberts

Tissue testing can be a valuable tool to help diagnose nutrient deficiencies or toxicities after visual problems alert us to a potential issue, but we can also use tissue testing in a proactive approach to make sure that nutrients are not limiting rice productivity.  Whether you are using a reactive approach or a proactive approach here are a few things to keep in mind.

After N fertilization and flooding through flag leaf emergence, the primary rice plant part that will be sampled for nutrient analysis is the Y-leaf.  The Y-leaf is defined as the uppermost collared leaf and is typically near the top of the rice plant and offset at ~45 degrees causing a “Y” shape.  When trying to diagnose a potential nutrient deficiency it is essential that 15-20 leaves are collected from areas of the field that are “Bad” along with 15-2 leaves from areas of the field identified as “Good”.  Having samples from areas that appear healthy and unhealthy will help to differentiate between potential problems. 

When using a proactive sampling approach, it is more important to get a representative sample from the entire management area of the field.  At least 15-20 leaves should be collected randomly from the entire field and composited to form a sample for nutrient monitoring.  Once samples are collected it is important to place them in paper sacks to initiate the drying process and every attempt should be made to get them to the lab for drying and analysis as soon as possible.

When using tissue sampling to diagnose deficiencies or toxicities, we use sufficiency ranges and critical concentrations that are usually based on survey data that has been collected across major rice production regions.  These critical concentrations and sufficiency ranges are almost always specific to a particular plant part and growth stage which for rice is typically the whole plant (from emergence to tillering), the Y-leaf (from tillering through flag leaf emergence) or the flag leaf (flag leaf emergence through maturity).  Collecting the correct plant part at a given growth stage is critical for proper interpretation of tissue nutrient concentrations as these critical values and sufficiency ranges often change as the rice crop matures due to dilution of nutrients with increased rice biomass.

In Arkansas, the most common nutrient deficiencies in rice post flood are nitrogen (N), zinc (Zn), potassium (K), sulfur (S) and phosphorus (P).  Although we may see deficiencies for other plant essential elements, they are extremely rare and usually the effect of some other management practice or recent land leveling.  As far as nutrient or elemental toxicities are concerned these are also quite rare and you are most likely to see a nutrient toxicity when another element is deficient.  For instance, rice will hyperaccumulate iron (Fe) when it is deficient in Zn.  In many cases Zn deficiency is often first seen as “Iron Toxicity” as the plant tries to overcompensate for the lack of Zn by taking up extra Fe.

A proactive nutrient monitoring program can be useful to stay ahead of the curve and catch nutrient deficiencies before they occur or in plenty of time to stave off any potential yield losses.  However, there is little data available to make in-season adjustments to nutrient management based on proactive tissue sampling.  If a nutrient comes back slightly above or slightly below the critical concentration, there is very little data to support the next course of action and very rarely when nutrients are near the critical concentration would nutrient applications be economical.  Preventing hidden hunger of N, K, and Zn would be my primary use of a nutrient monitoring program in rice simply because these are the nutrients that we have the most data concerning in-season management and have Arkansas data on when and how to correct hidden hunger.

Almost all samples that are submitted in rice or corn to diagnose a nutrient deficiency or for nutrient monitoring will come back deficient in boron (B).  Boron applications to rice and corn in Arkansas are not profitable and the interpretation of these B tissue concentrations is rarely useful for cereal crops.

As always, the best defense is a good offense (at least with nutrient management) and using proper soil testing and fertilization based on soil test levels will pay dividends in the productivity of your operation.  Being proactive in the management of soil nutrients is always the best course of action.  However, it’s always good to be on the lookout for potential nutrient deficiencies post flood as this is when they are most likely to occur and be “obvious”.  If you are concerned about potential nutrient deficiencies a tissue test may help identify potential hidden hunger.  Please remember that there is a wide window of opportunity for successful application of most nutrients (except Zn and S) from preplant to late-boot, but the earlier a potential deficiency is identified the larger the return on investment.

DD50 Rice Management Program is Live

The DD50 Rice Management Program is live and ready for fields to be enrolled for the 2023 season.  All log-in and producer information has been retained from the 2022 season, so if you used the program last year you can log in just as you did last year.  Log in and enroll fields here:  https://dd50.uada.edu.

Use the Arkansas Rice Advisor Internet App!

The Arkansas Rice Advisor site https://riceadvisor.uada.edu functions like an app on your mobile device.  There you can readily access the DD50 program, rice seeding rate calculator, drill calibration, fertilizer and N rate calculators, publications, and more.

Additional Information

Arkansas Rice Updates are published periodically to provide timely information and recommendations for rice production in Arkansas.  If you would like to be added to this email list, please send your request to rice@uada.edu.

This information will also be posted to the Arkansas Row Crops blog (http://www.arkansas-crops.com/) where additional information from Extension specialists can be found.

More information on rice production, including access to all publications and reports, can be found at http://www.uaex.uada.edu/rice.

Acknowledgements

We sincerely appreciate the support for this publication provided by the rice farmers of Arkansas and administered by the Arkansas Rice Research and Promotion Board.

The authors greatly appreciate the feedback and contributions of all growers, county agents, consultants, and rice industry stakeholders.