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Delta Farm Press
by Jarrod Hardke, Rice Extension Agronomist - June 9, 2023
“There’s something happening here, but what it is ain’t exactly clear.”
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
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.
“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,
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.
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.
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.
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.
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 email@example.com.
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.
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.
Rice Extension Agronomist
Extension Weed Scientist
Rice Verification Coordinator
Extension Rice Pathologist
Extension Soil Fertility