MI-07488 Revised 2005
After you've invested money to produce grain, make sure you protect that investment by managing grain properly in storage to prevent dry matter and quality losses due to mold and insect activity. Here are some tips for managing stored grain.
Clean Bins Before Harvest Grain and fines (small pieces of broken grain, weed seeds, and chaff) remaining from previous crops almost always contain stored grain insects. To reduce insect problems in the new crop, avoid mixing old and new grain. Also, clean bin walls and floors, the space under perforated floors, and the area outside of bins to remove old grain dust, fines, and kernels.
Manage Fines Fines cause problems in grain storage because they are more susceptible to mold and insect attack than are whole kernels, they restrict airflow during aeration, and they tend to concentrate under fill spouts during grain handling. Select and use grain harvesting and handling equipment to minimize the amount of fines in stored grain and consider using a grain cleaner to remove fines before the grain is stored. In addition to improving grain storability, research has shown that cleaning scab infected grain over a gravity table reduces DON levels in the cleaned grain. Fill bins in a way to prevent concentration of fines at the center. Use a grain spreader to distribute fines uniformly throughout the bin, or don't use a spreader and periodically withdraw fines from the center as the bin is filled (Figure 2.1).
Control Moisture Molds and insects need moisture to live and reproduce, so make sure the grain is dry before it is stored. Maximum recommended moisture content for wheat is 14 pecent (wet basis) for up to 9 months storage, and 13 percent for more than 9 months storage. Barley moisture should be 13.5 percent and 12.5 percent, respectively, for the same storage periods.
If grain is too wet when it is harvested, dry it with unheated (natural) air if the bin is equipped with a full perforated floor and a large enough drying fan. Recommended airflow values for natural-air wheat and barley drying are 0.5 cfm/bu (cubic feet of air per minute per bushel of grain) for 14 percent to 16 percent moisture grain, 0.75 cfm/bu for 16 percent to 18 percent moisture and 1.0 cfm/bu for 18 percent to 19 percent moisture (Table 2.1). Get a copy of the University of Minnesota Extension Service bulletin Selecting Fans and Determining Airflow for Crop Drying, Cooling and Storage, FO-5716, or download a copy of the FANS computer program from the Web at: www.bae.umn.edu/extens/postharvest for help in estimating airflow in bins. In general, operate natural-air drying fans continuously (24 hours/day) until all the grain in the bin is dry or until average daily temperatures drop below freezing. Tables 2.2 and 2.3 list the grain moisture content that can be attained based on the ambient temperature and relative humidity when using natural-air drying. If drying is not completed in the fall, run fans as needed to keep grain at 20 to 30 °F during winter, and resume drying early in the spring. Figure 2.2 illustrates the natural-air drying process.
Table 2.1 The recommended airflow for natural-air and low-temperature wheat and barley drying.
Table 2.2 Equilibrium moisture content (% wet basis) for hard wheat exposed to air at various temperatures and humidities.
Table 2.3 Equilibrium moisture content (% wet basis) for barley exposed to air at various temperatures and humidities.
Wheat and barley also can be dried in the types of heated-air dryers that were designed for use with corn, but you might have to reduce the drying air temperature to prevent grain damage. Keep grain temperature below 140 °F for grain used for milling, and keep it below 110 °F for grain used for seed or malting.
For more information on drying and storage, get copies of the University of Minnesota Extension Service fact sheets Wheat and Barley Drying, FS-5949 and Wheat and Barley Storage, FS-5947 or North Dakota State Univeristy Extension Service publications Natural Air and Low Temperature Crop Drying, EB-35, Grain Drying, AE-701, and Crop Storage Management, AE-791.
Aerate to Control Grain Temperature Dry grain should be cooled to less than 60oF as soon as possible after harvest by operating aeration fans during cool weather. In late summer, this might mean running fans only at night. Don't worry too much about high nighttime relative humidity during aeration because grain rewets much slower than it cools.
In late fall or early winter, use aeration fans to cool the grain to 20 to 30oF for winter storage. If grain is not stored at less than 20oF during winter, you shouldn't need to run fans to warm the grain in spring. If you do run fans in the spring, start early in the season (March or April) and make sure you don't warm the grain beyond 40 oF. Cooling grain limits mold and insect activity and it reduces moisture migration. Moisture migration can result in rewetting and eventual spoilage of the grain at the top center of inadequately cooled bins (Figure 2.3).
Estimate the number of hours a fan must be operated to cool a bin of grain by dividing the number 15 by the airflow in cfm/bu. For example, in a storage bin that has an airflow of 0.2 cfm/bu (a typical value for farm bins), it takes about 15 / 0.2 = 175 hours, or about three days of fan operation to cool the grain. See the University of Minnesota Extension Service bulletin Management of Stored Grain with Aeration, FO-1327 or the North Dakota State University Extension Service Publication, Crop Storage Management, AE-791, or get a copy of Managing Dry Grain in Storage, AED-20, from the MidWest Plan Service for more information. Figure 2.4 illustrates how grain cooling occurs and how to check for completion of cooling.
Check Stored Grain Regularly Every two to four weeks in cold weather and every one to two weeks in warm weather, measure the grain temperature and moisture, and look for moldy, discolored, or crusted kernels, and for signs of insects. Permanently installed cables that hold electronic temperature sensors can make checking the grain temperature much easier (Figure 2.5). Also, start the fan briefly and smell the first air to leave the bin for musty or sour odors. If problems are detected, run aeration fans to cool the grain. If aeration doesn't control the problem, unload the bin and clean, dry, feed, or sell the grain. Wear a dust mask designed to filter mold spores when you handle moldy grain to avoid health problems.
Storage of Scab-Infected Grain University of Minnesota research on the storability of grain infected by Fusarium head blight indicated that infected grain deteriorated slightly faster in storage than did grain that had been cleaned on a gravity table to remove scabinfected kernels. But the differences in storability between cleaned and uncleaned grain were relatively small. This means that instead of selling scab-infected grain at a low price during harvest, careful grain managers can store the crop and wait for better marketing opportunities. There was so much sample-to-sample variability in DON (deoxynivalenol or vomitoxin) measurements taken during the study on storage of scab-infected wheat that no conclusions could be drawn about changes in DON during storage. The fungus species that causes scab infection and produces DON remained viable during storage at 18 percent and 20 percent moisture, but this fungus species died during storage at 16 percent moisture. This means that DON production during storage is unlikely for wheat stored at less than 16 percent moisture.
Authors: William Wilcke and Kenneth Hellevang
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