Episode 17 - Drain Timing for Flooded and Furrow-Irrigated Rice (8-19-20)

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, let’s talk a little bit about drain timing on rice — always a fun and interesting topic. A lot to think about and often referred to. It’s as much of an art as a science to determine the proper time to drain rice. 

One avenue that we certainly have is the DD50 rice management program. It’s going to give you a predicted draining date. That predicted draining date essentially adds 25 days to the date of 50 percent heading for long-grain cultivars, or it adds 30 days to the 50 percent heading date for medium-grain cultivars. 

So that’s going to be the first jumping off point, is that number of days in addition. So if you’re looking at a year or an occurrence where for whatever reason, by the time the plants actually reach 50 percent heading differs a little bit from the report, whether that’s, “Did we get the emergence state just right?” or “Did we get fertilized and flooded late?” It may push that date off a little bit, normally catches up even pretty close, but it can happen. It can push off by a few days, so we want to start with that consideration of that rough number of days to put us in the ballpark of when we’re probably going to be in pretty good shape to drain. 

From there, once we’ve gotten close to that date or around it, we want to have a closer look by soil type at what we’re dealing with. So on a clay or clay loam, just a pretty heavy soil type, stays really wet. We’re really looking for at least a third of that panicle to be hard dough or what we call straw-colored kernels — you know, yellow, tan — it’s going to vary by cultivar that exact color. We’ll just say straw-colored kernels. At least a third on heavy clay. If you want to lean a little more conservatively toward a half, we can certainly do that. 

On a silt loam soil, we’re really looking at more like two-thirds to three-quarters straw colored. Again, getting a lot further along because that soil is going to dry out a lot faster once we take the water off of it and start to shut things down.

One kind of key component for me on that is if I’m looking — pick whichever soil type you’re on with this thought process — but for whatever rough percent straw-color maturity you’re looking at or wanting to achieve in a field, if you’re looking at it and you’re not sure if you’re at that point yet, that just means we’re waiting a few more days, whatever it’s going to take. Don’t go ahead and pull the rods or the sticks then. Probably need to wait a few more days until you’re sure, again, with that goal to lean a little more conservatively from the drain timing, just to make sure we don’t pull things out too early. 
And, of course, we’re always acting like when we take the water off that it’s never going to rain again. So that’s part of the conservative lean. If the forecast is full of rain, you may pull it just a little bit early, but this year’s been a good example of high percent rainfall chances later in the summer that never really dropped much rain at all. So again, forecast is great but can’t always be depended on. So we’ll lean a little conservatively in that regard. 

With probably over 200,000 acres of furrow-irrigated or row rice out there this year, definitely coming in with more questions about drain timing on furrow-irrigated rice. It seems like a misnomer — if it’s furrow-irrigated, what are you draining? — but of course in a lot of these fields where possible, we are holding and backing water up, and blocking and backing water up in the field. And certainly there’s been very little, if any, work on this subject of drain timing, but if we kind of just take a step back and think about it — I think from a logical standpoint — once you get to that rough drain timing again and going back to days after 50 percent heading and approximate straw color that we’re looking at for draining, we can let that water go from the bottom and start moving that direction. That large amount of water in some cases, that if you were holding and start getting that off the field, but in reality you’re probably going to want to irrigate that field one more time at least one more time after that drain date —primarily that upper portion of the field. 

You don’t have a full soil profile full of water. At this point and time again, it’s going to dry out very quickly. We want to avoid that upper end getting too dry too fast and starting to shut down and potentially cave in and shatter too early before we’re ready to go get it,  and especially before the bottom end is ready so we can get it all out. So that’s just a generalized ideal.

Irrigate one more time past the drain date in furrow-irrigated rice. Again, we’re trying to lean conservative there, and if you are holding water at the bottom, you can still turn that loose at roughly the same time we’re talking about draining flooded fields. But again, it’s still going to see water one more time. We’re just going to have an easier time getting that remaining  water off and gone. 

So, anyway, just the quick recap using DD50 program to give you an approximate number of days out to drain when we can start looking at that straw color of the kernels, whether that’s a third to a half straw color on a clay type soil and two-thirds to three-quarter straw color on a loamier type soil in that situation. Again, probably irrigating one more time after the rough drain date on furrow-irrigated rice is really what we’re shooting for in this scenario. 

So again, this is Jarrod Hardke, rice extension agronomist with the University of Arkansas System Division of Agriculture, and thanks for joining us one more time 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