Mid-South producers are building more and more bins for on-farm grain storage. While the practice allows much greater opportunity to take advantage of higher market prices and harvesting flexibility, it does come with some risk.
In Arkansas, currently, some 80 percent of rice is dried commercially.
“Concerns with mycotoxins and kernel discoloration aren’t really too great because the rice is usually dried fairly quickly,” says Terry Siebenmorgen, University of Arkansas food science professor. “The concern there is if it’s dried too quickly it might lead to some milling reductions and possible stain. But most driers do a very good job avoiding those problems.
“The potential worry now is with the increase in the use of on-farm drying systems in which grain is dried over extended periods of time. Sometimes grain with high moisture content just has to be harvested and brought in. So, how best to deal with those circumstances?”
The proper use of those systems -- commonly called “in-bin drying systems with equilibrium moisture content (EMC) controllers” -- is the focus of Griffiths Atungulu’s research.
“With these in bin systems, weather conditions often are a major factor in how quickly grain dries,” says Atungulu, University of Arkansas food science assistant professor. “When you have bins 40 feet high and grain being dried very slowly, it can mean the top layers of grain stay at high moisture content for long periods of time.
“You should assume that the grain entered the bin with some mold that can cause mycotoxin. If the grain is not dried quickly, the relatively high moisture content of grain provides a safe haven for that mold to multiply. Because of that, there’s high potential for mycotoxin production.”
One thing that has spurred the research is new bin ‘cableing’ technology. “It involves very strong cables placed in a bin that allows a grain producer to monitor, at any time, the temperature and relative humidity both radially and up-and-down in the bin,” says Atungulu. “The temperature and relative humidity readings allow for calculation of the moisture content; this technology is a great development. It should allow very energy-efficient drying and better quality maintenance.”
The Brantley family operation in England, Ark., has been using cableing for four years. “It’s superior and we really like it,” says Dow Brantley. “I don’t think we’ll ever go without it.”
The Brantleys began growing corn in 2000 and built their first bins in 2003. “Originally, we brought corn in as a rotation crop with cotton. We’d been growing cotton in some fields for 20, 30, 40 years consecutively and needed to change things up desperately -- something to help pick up our yields. That coincided with the time that many farmers had begun to struggle with cotton.”
The operation now has a bit over one million bushels worth of storage for corn and rice. “That continues to grow with the farm and business. When we put up those first bins, we never thought we’d end up adding so much more.”
It’s all due to the marketing advantages the family has realized. “We didn’t know how much of an advantage it would be when we put the first ones in. But it’s proven to be tremendous.”
There’s an advantage beyond marketing, though: efficiency.
“It’s hard to take that to the bank and put a number on,” says Dow. “But it’s really great to be able to keep from having to wait in long lines and be able to harvest when you need to.”
The Brantley crews “haul every day. That has created some jobs. We keep corn year-round -- we haul our last bushel off when the first bushel of the new crop is coming in.”
The operation primarily provides grain to the poultry and hog industries. Grain deliveries to hog farms occur on a weekly basis.
Once rice is in the bin, fans typically pass outside air up through the grain mass. The lower layers of grain in the bin dry first. The drying progresses up the bin until, eventually, the drying front reaches the top. With an EMC-based control system, the fans will only run when there’s drying potential in the air, i.e. when the EMC associated with the ambient air conditions is between set limits that allows drying, and avoids over-drying.
That’s why the weather is so crucial to the drying process.
“If there are a lot of days with dry air, the grain will go ahead and dry down,” says Siebenmorgen. “But if the weather isn’t conducive, that can be a big problem.
It’s certainly much better to deal with mold than with mycotoxins, says Atungulu. “There are different types of mycotoxins that can develop from mold or fungal attack on grains. Some can occur in crops still in the field. Producers are probably familiar with diseases like leaf blight and others.
“Moving the grain into storage allows the growth of certain molds that do better in bins. One of the mold families that do this in rice is Aspergillus flavus, which could contaminate the grain in the field. After the mold grows on the binned grain it can cause aflatoxin under certain stressed conditions. That’s the most carcinogenic compound yet found related to food. The FDA says grain with about 20 parts per billion cannot be used for human consumption but must have an alternate use or be disposed. If it is to be used as animal feed – such as cattle, swine or mature poultry -- the requirement is that the aflatoxin must not exceed 100 parts per billion. That shows how toxic aflatoxin is.”
One of the things Atungulu and colleagues will look at in their research is the drying potential for bin systems placed in different geographical regions, and assess and map out the risks associated with grain quality reduction and mycotoxin contamination during drying and storage. “Assuming you have grain at high moisture content for a prolonged period, how does the mold develop in different regions and bin configurations? Once we identify the rates of harmful mold growth and mycotoxin development in different bin drying and storage scenarios we can go to farmers and say, ‘Okay, you’re at this geographical location and have these expected weather conditions so be careful. There’s a high risk of mycotoxin development if you place grain above this critical moisture content in the bin.’
“We want to give the farmers ideas about the best practices based on locations and bin set-up. If we can do that it would help farmers mitigate the chances of mycotoxins.”
Siebenmorgen elaborates: “Some of the practical information that we hope comes out of this research will just give farmers proper guidance based on a given area. Rice dried in northern Arkansas faces different conditions than rice in southern Texas. What is the maximum moisture content that rice should be placed into a bin? It’s complicated because of the depth of rice in a bin, the horsepower of the fan, the air that’s going through the bin, all of that comes into play.”
What if the mycotoxin does occur?
“Right now, there’s nothing you can do to decontaminate or detoxify the grain,” says Atungulu. “My research will look at different ways we might detoxify such grain.”
“We want to prevent mycotoxins, period,” says Siebenmorgen. “But if it does develop it would be nice to have an alternative means to salvage the grain. Griffiths has done work with infrared drying that appears to have promise.”
Atungulu and Siebenmorgen are keen to thank those funding the research. “We’re fortunate to have financial backing from the Arkansas Rice Research and Promotion Board, the Arkansas Corn Research and Promotion Board and also the Arkansas Soybean Research and Promotion Board. They’ve been very generous and we’re very thankful for their foresight.”