Arkansas Rice: Time to Flood? Weather Causing Shifting Management Strategies

    Young rice crop. ©Debra L Ferguson Stock Photography

    Crop Progress

    Flush’em if you got’em.  It’s hot, and it’s dry.  The current conditions of highs in the upper 80s to low 90s look to continue until some rain chances late next week.  The heat means great things for rice progress, but it’s going to need a little help to keep trucking along with these winds taking all our moisture away.

    Some much improved conditions last week saw a major jump in planted progress to nearly 80% while emergence progress is up near 50% (Fig. 1-2).  Add in spotty rainfall and flushing this week and we have a lot more to a good looking stand than many thought we would achieve.

    The interesting part is we seemingly have a lot of rice that went from barely emerged to 2-leaf rice.  It was growing and trying to emerge and now that it has been fully turned loose, it’s progressing fast.

    A good recommendation for an increasing number of fields is to spray herbicide and flush, then as soon as it dries up the rice will be big enough to fertilize and go to flood.  Some fields are going to flood this week!

    Fig. 1. AR Rice Planting Progress 2007-2018.  Click Image to Enlarge

    Fig. 2. AR Rice Emergence Progress 2007-18. Click Image to Enlarge

    Time to Flood?  Check the DD50!

    We’re getting really close to needing to take fields to flood (some already going) so it’s a great time to check where you are based on rice development.  Run reports here.

    As of right now, in Table 1 are some examples of optimum and final times to apply N based on emergence dates at different locations in the state from the DD50 program (using Diamond as an example).  Keep in mind that you need to run your own reports based on specific cultivar, location, and emergence date.

    These predictions are based on 30-year weather averages, but each day that passes the average data is updated with the actual day’s weather to be increasingly accurate.

    Table 1. Current preflood N application timings based on DD50 accumulation at different locations in the state for Diamond. Click Image to Enlarge

    Why We Apply N the Way We Do

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    Based on some questions received recently, it’s a good time to review why we manage nitrogen (N) like we do in rice. Applying N immediately prior to flooding serves two very important purposes: 1) it incorporates the N into the soil where the plant can better take it up, and 2) it reduces N loss.

    If N as urea is left laying on the ground, the loss is much greater than if it is incorporated into the soil and held there by a permanent flood.  If you put a large amount of N on the ground well prior to establishing the permanent flood, you’re going to experience a great amount of N loss before the plant gets a chance at it.

    Some out there have already, or are thinking about, putting a large amount of urea around planting or at the 2-leaf stage.  The earlier urea is put out prior to flooding, the greater amount of N will be lost.  This will make managing N to maximize yield that much more difficult, and we’ll end up over-fertilizing to compensate for the unknown amount of loss that’s occurred.  Table 2 illustrates how little N we take up from a pre-plant incorporated N application timing versus the same rate applied preflood.

    Table 2. N uptake efficiency and grain yield by N application timing. Click Image to Enlarge

    Weather You Like It Or Not…

    As the hot, dry weather works its magic for growth it’s also creating stress situations and changing management strategies.  For herbicide applications to go out right now, and not be followed by a flush or a flood, it’s a waste if you’re spraying residual products.  That is not to say that no herbicide applications should be going out, just that we need to pick and choose.

    An application of a residual herbicide such as Command or Prowl is just going to lay there in this heat and sun and waste away.  At the moment we’re about 7 days away from any forecast rainfall.  If you’re going to spray the residuals, you need to flush or be going to flood, or keep them in your pocket.

    If you need to spray right now and you refuse to flush in the residual (and you aren’t ready for flood) then it’s best to go across with a post-emergence herbicide like propanil for now.  Then come back with residuals and anything else you need ahead of a rain, flush, or flood.

    The topic has come up that some folks are just going to wait around until just prior to flood to spray again and then clean everything up with Loyant like it’s a magic wand.  Some of these fields already have 3-leaf barnyardgrass and 2-3 leaf rice.  How big do you think that grass is going to be by flood time?  How big are the other weeds going to be that Loyant doesn’t get?

    There is no such thing as a true “salvage” herbicide.  Most are used as “revenge” herbicides that perform poorly because we ask too much of them under the worst conditions.  If we start treating Loyant this way right off the bat, we may send the new herbicide packing in a hurry.

    Speaking of Loyant (again)…

    Be Careful of Loyant Drift On Soybean

    The label for Loyant states that it should not be applied to rice when wind is blowing toward adjacent soybean fields.  There is not distance restriction other than “adjacent” but be careful with this.  Loyant is non-volatile and so far seems to stay put, but it will drift with wind.

    Injury to soybean can be severe in drift situations, but not as severe at extremely low rates as some ALS chemistry such as Regiment.  Fig. 3 shows soybean injury in demonstration plots last year.

    Fig. 3. Loyant injury to soybean at a below labeled rate.

    Bug Alert!  For True Armyworm

    Reports out of northeast Arkansas for true armyworm attacking seedling rice and mowing it back to the ground.  Get out and scout around field edges, especially near wheat or tree lines.  During the heat of the day, they’re likely to be hiding under clods and in cracks, don’t assume they’re gone!  Dig around and you’ll find them, even under small clods.

    Treatment when injury is severe should be made either very early morning or late afternoon / evening to take advantage of their nighttime feeding behavior.  Pyrethroids work extremely well – you won’t necessarily have to use high end product rates.

    Fig. 4. True armyworm feeding on seedling rice near field edge.

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