Episode 15 - Foliar vs. Soil Applied Nitrogen Fertilizers in Rice

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

Jarrod Hardke: Welcome to Arkansas Row Crops Radio. I'm Jarrod Hardke, Rice Extension Agronomist for the University of Arkansas System Division of Agriculture.

Today's episode is about foliar versus soil-applied fertilizers, getting quite a few questions on that topic these days as a lot of rice is in the mid-season timings and moving into light boot again, primarily focused on the nitrogen aspect at this point in time. So, one of the biggest items there to jump into is that there's very little research at this point in rice to support the use of foliar fertilizers. Certainly, could be possible that they could be used to supplement a good fertility program. And there may be some ways that they can help to recover from other issues going on, but certainly not something that are getting leaned on. One problem with attempting use a foliar product, again, in place of more of a soil-applied urea, for instance, product, is that the foliar products really only carry small amounts. So, if you think in terms of a product that's a 32 percent nitrogen, for example, its got 32 percent nitrogen, well that products probably only a 10 pound per gallon weight. So, 32 percent of that is only three-point two pounds of nitrogen in there. So, when you compare a gallon or even two gallons of that product, so be in 3.2 or 6.4 pounds of nitrogen going out vs. 30 to 45 pounds of nitrogen as urea being applied at a mid-season to late boot timing depending on variety or hybrid, there's a big difference there. A frequent comment that we hear along those lines is well the foliar's taken up with a really high efficiency. The problem with that is, you know, really high efficiency that you know what, 70, 80 percent efficiency sounds great. Sounds really high. Well, our mid-season and late boot applications of urea are taken up with a 70 percent or greater efficiency when we're putting those out. So, again, getting 70 percent of 30 to 45 pounds of nitrogen versus 70 percent of 3.2 or 6.4 pounds, big difference in amount of nitrogen. And there are some charts floating around out there. Then, you know, trying to say that one pound of nitrogen applied foliar is equal to 5 to 10 pounds of nitrogen applied to the soil and that's really just false. A pound is a pound. And when we talk about being a plant, again, being able to take up 70 percent of 30 pounds of nitrogen versus 70 percent of 6.4 pounds, there's a massive difference in the amount of nitrogen getting into that plant at those times. So, there are some additional issues with those applications, particularly as it relates to, again, nitrogen-based products and again, trying to piggyback with fungicide applications, things like that. There's a there's a real potential to see some foliar burn with some of these products, probably more likely to actually see burn two exposed heads if we're just starting to get the heading. And when you're talking about putting a couple of gallons of a half percent nitrogen product into an aerial application, that's only going to be probably at 3 to 5 gallons per acre, that's a whole lot of product and not a lot of water to cut it in that situation. So, we've seen spots where exposed heads get lit up pretty good and blanked out again, less so the leaves that are more mature and waxy but that can happen too. So ultimately, we want to continue to use the soil-applied fertilizers in this case, urea at midseason for varieties, and at late boot for the hybrids to properly manage our crop needs. We have a high efficiency of uptake and use of those timings and rates applied to varieties and hybrids. So that needs to continue to be our focus for optimal crop management, for both yield milling and standability, depending on what all we're making an application for.

So, with that, it's been a little overview of foliar versus soil-applied fertilizers focusing on nitrogen in really reproductive stage rice. And if you have any questions, feel free to reach out to us or your local county agent. And thank you for joining us once again on Arkansas Row Crops Radio.

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.edu