Episode 5 - Rice Milling Issues

Arkansas Row Crop 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 rice milling issues. Over the past several weeks, there have been a lot of questions come in regarding rice milling yields, specifically head rice yields. 

Ultimately what we've had going on as we entered August and really were able to get started with harvest, we got really hot. A lot of people referred to it as a late summer this year for 2019 after much of the year was extremely mild. And with that high daytime temperature still relatively low, nighttime temperatures not getting too high, but it got extremely dry with those high daytime temperatures. And ultimately from there the grain in the field dried very, very rapidly over that period of time - really surprised a lot of people just how fast it could drop. 

For a little bit of background, the wealth of data that the Division of Agriculture has been able to accumulate on the effects of infield drying on milling yields really suggests that for long-grain cultivars, optimum milling, more specifically head rice and total rice yields, they really optimize in the 19% to 21% moisture range. Now for many, that's a little bit too high. Taking into consideration drying charges or even the ability to dry grain that is still that wet, if it's going into on-farm storage. But again the data does support that that's when milling yields remain the highest. For medium grains its actually even higher at 22% to 24%. Again, not necessarily something that's achievable in the field and with our current commercial equipment to dry and to handle, but pointing toward higher moisture contents when they're taken out of the field leading to higher milling yields, kind of the take-home point there.

Ultimately what we ended up seeing is really through August and a good portion of September with that continued heat and dry weather, even though the grain was drying very rapidly and to considerably low moisture, even taking green rice out of the field at well below 15%, even some being delivered at 13% and still seeing some very good head rice yields at that point. And the way to explain that is that in yet another oddity of the 2019 season, that extreme dry weather with that heat, the reason we typically see declining head rice yields when grain is allowed to dry down in the fields for too long is that with rainfall events or even just heavy dew periods because of high humidity that grain is drying down and then it will get rewet and then as it is rewetted it will dry back out, and as it cycles through that wetting and drying, fissures can form in those kernels. And those fissures are going to turn into breakpoints in the milling process, and that's where you're going to have the kernel come apart in milling. When you are under extremely dry conditions, temperature, humidity, and no rainfall anywhere to speak of, you're not having the severity of those wetting and drying cycles, so we were able to actually fall way below traditionally what we would be prepared to tolerate and keep reasonable milling yields. We fell way below that. Still looked pretty good, everybody was pretty comfortable with those milling yields, then about three weeks ago, things changed again, some rainfall came back into the system. The temperatures dropped a little bit, humidity came back up, some rain came back in, all of a sudden we had some pretty good rewetting events and some heavy dews come back into the picture along with it. From that time over the past three weeks, those head rice yields have really taken a big hit. The worst-hit, of course, was any grain that was already extremely dry sitting out there in the field. That's where the most dramatic hit occurred and really is as we continue to move from here, I mean a big part of it was we simply could not harvest as fast as this rice got ready because of that heat throughout August and September. There's not much we could do about it. And really not to do from here but to say continue hammering away and get it out as quickly as possible to minimize those declines. Once it's out of the field, in the bin, in somewhere that decline is not going to continue. So we need to get it put up.

But from here, again that doesn't solve a lot, but there is grain still out there that now that we've hit this slow down window, some are hung at a relatively high moisture. The later planted rice that some of it was planted at the very end of May into the first part of June is actually hung in place now not wanting to drop in moisture. The danger there is that conditions may be showing that it's staying at a relative moisture, not dropping. The reality is that's probably surface moisture held between the kernel and the hull. It probably is dropping more than we anticipate, so be prepared for that rapid drop. Once it starts to go its probably going to go fast because that moisture content you're able to measure is probably pretty artificial. We've seen that in recent years and that occurred even during the fall of 2018 during one roughly 10-day period and it looked like nothing was drying, but suddenly the right conditions hit for two days and in a two-day period 5% moisture drops were observed in some rice, telling us that drying was actually happening. Our equipment is just not set up to measure some of those differences and where the moisture is, whether it's inside the kernel or being held within the hull. 

So as we move forward, we need to continue to focus on attempting to harvest at those slightly higher moisture contents. Again we were outrun by the crop this year after waiting forever to get it in on the front side then it chose to outrun us on the backside, so were dealing with that but that's ultimately where a lot of the issues have come from, and the way around that again is to just get it out as fast as possible.

So if you have any questions further regarding rice milling yields or anything along those lines, feel free to give us a call, reach out to us and maybe we can help answer any further questions that you have or if there's any other topic going on out there or for harvest season that you think you think we can help with, give us a call on that one as well. 

And with that, thank you for joining us once again on Arkansas Row Crops Radio. See ya next time.

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