Title: Rice and Advice, Ep. 03: Managing Preflood Nitrogen with Wet and Rainy Conditions (6/3/21)

Arkansas Row Crops Radio, providing up to date information and timely recommendations on row crop production in Arkansas.

Welcome to Arkansas Row Crops Radio. IÕm Jarrod Hardke, rice extension agronomist for the University of Arkansas System Division of Agriculture. Today on Rice and Advice IÕd like to talk a little bit about managing pre-flood nitrogen in wet and rainy conditions. I think most of us can relate to those conditions really for most of the spring, but now that itÕs time to actually start getting a lot more rice to flood some of the earliest rice has already gone there and was able to take advantage of a few limited early drier windows to actually get nitrogen out on dry soil the right way, the way we prefer and recommend, but now a lot more rice that was planted in mid to late April, depending on where you are in the state and a little bit since then really getting to that point of we really want to take rice forward and then try to fertilize and flood, the topic of today. 

So the first obvious piece of advice is to run a DD50 report and for those of you listening IÕm sure most of you are aware but DD50 is the degree day 50 program where we use heat units to monitor to measure the growth and development of the rice crop. Those are cultivar specific and based off of emergence dates to give us predictions of when we should reach approximate dates and of course one of the most important dates on there is that early season pre-flood nitrogen management timing that weÕre so much focused on. As a general reminder if you had rice that emerged on the fifth of April and you ran a report that day, then everything predicted from then was based off of at least ten, but in some cases thirty year weather averages for the future so every day, every night, that program updates itself from the previous days actual weather so it gets more and more accurate as it goes. So if you havenÕt run one of those in while and youÕre still using the old dates, you might want to rerun that because itÕs actually probably going to give you another two or three days to each of those timings because rice has been growing so slowly compared to average with the cooler temperatures and the rainfall. So again, run the DD50 report, look for that final recommended time to apply pre-flood nitrogen. ThatÕs what youÕre after and that date really is your friend because it tells you that last time you can wait until. We certainly donÕt prefer to always get to that date or wait that long. We want to move that crop along earlier if we can, but again rice has been shorter this year given the cool temperatures and the cloudy conditions and so weÕve had to wait a little bit longer anyway just to get the size we would like to be able to put a flood, so look at the final nitrogen date. There is some room built in beyond that date to account for the time to establish the flood. So thereÕs already a little bit of a fudge factor in there, but as we know we donÕt just put the nitrogen out and snap our fingers and have a flood on the field. WeÕve got a little time we have to have in there to get that accomplished. So thatÕs there to be accounted for. But in these scenarios weÕre talking about with the sub-soil, sub surface still being larger saturated even if we are drying a little bit at the surface, weÕre going to flood fields a lot faster and easier than under our more traditional, more very dry soil conditions when weÕre trying to put out pre-flood nitrogen when we get our way. But then again use that final nitrogen date as your trigger to make a decision on doing something. As we pass that date basically sitting still means youÕre going to start moving backwards in terms of yield potential, so as we get to that date weÕve got to decide to act and do something and that kind of brings us really to where we are today with fields that are to that date or getting just past that date even with some of the questions that have been coming in. So to start out get the recommendation part of all this is the preference is always to get urea to the soil surface. ThatÕs the preference. Obviously dry is number one and thatÕs the primo way to go, but again having a lot of trouble finding that right now. So really the take home is the firmer the soil the better, but again we keep getting rain and so weÕll take a muddy condition if thatÕs the best that we can get. Now whatÕs muddy to me, whatÕs muddy to you, the biggest part is get rid of the standing water. Yes some of your bar ditches, your levee ditches may have some water in them a little bit, but again the majority of the patty, the flats out there, having standing water essentially gone, we donÕt the urea landing in standing in water, it can land on the mud and we can work with that and the goal is to get to that point where we can get it applied to, at worst, a muddy soil surface and try to let that soil dry underneath that urea as long as it can until the next rain and if you miss a forecast rain that was supposed to be there pretty quick, the it can actually firm up pretty decently for a few more days, even better and then we can start bringing the flood but if you do get it out there and itÕs muddy, get the rod set, everythingÕs otherwise ready to go, the gates are ready and if it does start to rain, then weÕre just going to go ahead and start pumping. When weÕre making those applications to muddy soil, essentially the muddier it is, the less time youÕll have to dry it out or at least the less time youÕll think you have to dry it out. Consider increasing that pre-flood nitrogen rate by ten to twenty pounds of nitrogen per acre, ten to twenty units nitrogen per acre. Some work weÕve done over the previous few years have shown that again because itÕs a less efficient by going onto that muddy soil, that slight increase does seem to help offset some nitrogen loss that weÕre going to have by applying it to a more damp muddy soil condition. The less time you have before you think youÕre going to get that next rain and to allow you to dry out the higher you want to lean on that rate, that increase above your normal pre-flood rate. Again this will help offset losses due to inefficient incorporation that are going to come with putting a flood onto muddy soil. ItÕs not going to be driven down as quickly and deeply into the soil as it would if we were on dry soil. On muddy soils always remember to use a urease inhibitor, urea plus NBPT such as in Agrotain or some other recommended product like that. Just use an Agrotain as an example. The other situation of course, youÕre ready to go to flood and you catch a free one and so suddenly weÕve got stacked up water of inches in a field and so well at that nitrogen date or beyond, the final nitrogen date or beyond that start talking about that fun topic of spoon feeding which nobody is too overly excited about but we do get in that scenario sometimes and we can make it work. If weÕre talking about hybrids, really we know that weÕre going to need to spoon feed three weekly shots of a hundred pounds of urea. Once a week, a hundred pounds, three times. In some limited conditions we do see a benefit from a fourth application of a hundred pounds, but most of the time three shots is generally getting the job done and again thatÕs all talking about the early nitrogen. WeÕre still recommending the sixty five pounds of urea at late boot on those hybrids. For varieties itÕs going to be four weekly shots of a hundred ponds going out in a spoon feed situation and sometimes a fifth may be needed. And again from some work weÕve done, same thing as the muddy soil conditions, also on the spoon feeding approach, I saw plenty of instances where that fifth application of a hundred pounds could really finish bringing that yield potential on to the top for varieties impeticular and again certainly those timings are going to coincide with some of the mid-season timings for varieties and take care of that. When weÕre dropping urea into the water thereÕs no need to use an NBPT type product on that urea, itÕs not going to have any value when itÕs dropped directly into a standing flood so thatÕs one little bit of savings that we can have in that scenario. Again, wet and rainy conditions forcing us to go to more of a muddy or flooded situation is going to require us to use more nitrogen in these scenarios that is going to increase costs but we know that we can still achieve optimum yields in these situations. Again weÕre just kind of dancing with the partner that weÕre handed at the time. Just to reiterate, waiting too long for the ideal conditions, just continuing to wait for that dry soil and get it out that way, it just continues to lead to greater yield loss potential. From a general observation the hybrids have a, hybrids and varieties both begin to as you get past that final recommended date to apply nitrogen, they all generally start to decline very shortly after that. Again remember we built in just a little fudge time to get a field flooded that they all generally start to decline, but the hybrids decline a little more gradually. They are not going to make you pay quite as much most of the time as the varieties are going to start to trend down a little bit faster but again under especially not just the wet but the really cool conditions weÕre under and things just not growing off or showing how, showing their age as much. That could possibly fool you sometimes so going back to that DD50 report and the dates and again looking back at that DD50 to determine where you are and where you need to go. And just as important if youÕve got simply complicated scenarios, feel free to give us a call, shoot us an e-mail or text and run some of those situations by us and weÕll try to do our best to give you a more situation specific recommendation. Hopefully some of these general guidelines and recommendations will help you along the way keeping the rice crop moving and keeping our overall yield potential all the way up and hopefully things will straighten up very soon and weÕll get this behind us and rock on through yet another really good high yielding season.

Once again IÕm Jarrod Hardke. Thanks for joining us on this episode of Rice and Advice on Arkansas Row Crops Radio. Have a rice day. 

End notes: Arkansas Row Crops Radio is a production of the University of Arkansas System Division of Agriculture. For more information please contact your local county extension agent or visit uaex.uada.edu