Post-Harvest Handling of Organic Grain
Wheat and small grain harvest is fast approaching, if it has not already happened on your farm. This article, partially extracted from the North Carolina Organic Commodities Production Guide, will hopefully provide good tips for storing and keeping good quality grain.
Storing organic small grains is often critical for marketing that product. Buyers often do not have sufficient storage capacity and/or cash-flow to accept an entire crop at one time. A crop may need to be stored for several weeks or months, even up to 11 months, to meet market demand. Often, a better price for the grain is offered months after harvest, so storage may also be an economic advantage, as well. To maintain grain quality during storage, insects must be kept out and the grain must be stored at proper temperature and moisture conditions. Split operations (conventional and organic) will need separate storage bins, or storage bins will need to be thoroughly cleaned (swept, vacuumed, blown out with pressurized air, or all of these) to prevent commingling of organic and conventional products. Storage bins should be labeled as organic, and records of their contents must be maintained.
The best way to manage insect pests in stored organic grains is to avoid them. It is important to prevent problems in stored grain by keeping bins, ducts, and augers clean and by storing grain at a temperature lower than 60°F and at low humidity. Another suggested and often used method to prevent insect pest problems in stored organic wheat and corn is to add food-grade diatomaceous earth (DE) to the grain as it is being loaded into the storage bins. Diatomaceous earth can be sprinkled on top of the grain while it is moving in the auger to the bin, and then on top of the grain after it is loaded. Insecto is one brand name of DE that can be used in organic operations. The surface of each particle of DE is very sharp on a microscopic level, and these sharp edges cut into worms as they feed or move over the grain, causing them to desiccate. Be sure to talk to your grain buyer and certifier before using DE as a storage additive, and following label recommendations. To identify insect pests of stored grain, see the North Carolina Organic Commodities Production Guide.
Handling Stored Grain
Stored-grain management is a long-term approach to maintaining post-harvest grain quality, minimizing inputs, and preserving the integrity of the grain storage system. To implement an effective management program, you must understand the ecology of the storage system. Storage management must focus on the following factors:
- Grain temperature
- Grain moisture
- Air relative humidity
- Storage time
An excellent preventive postharvest grain management approach is the SLAM system (Sanitize/Seal, Load, Aerate, Monitor).
Sanitize and Seal
- Housekeeping—clean bin, aeration ducts, and auger trenches where insects thrive on dust and foreign material
- Cleanup—clean up around the bin, removing weeds, trash, and moldy grain.
- Seal bin—seal all openings to provide barrier protection again insect entry at all locations below the roof eaves.
- Load clean, dry grain—High levels of grain moisture increase the potential for high populations of stored-grain insects and molds. In North Carolina, corn that will be stored for more than 6 months should be dried to 13.5 percent moisture.
- Core the grain—This involves operating the unload auger to pull the peak down and remove the center core of the bin that contains the most fines and small foreign matter.
- Spreading or level grain — A level grain surface is easier to manage and less likely to change temperature during storage.
- Maintain grain temperature—Grain temperature should be below 60°F to control insects and mold. Grain temperatures should be reduced to the optimum storage level as early as possible following harvest, and grain temperature should be managed by aeration of grain in the fall, winter, and early spring. The aeration time necessary to achieve 60°F will vary due to the airflow rates of the equipment used and ambient temperatures. Aeration can also reduce grain moisture content from ¼ to ½ of 1 percent during one aeration cycle.
- Use aeration to prevent moisture migration—In most grain bins, moisture migration occurs due to significant temperature differences that develop within the grain mass. These temperature differences are caused by changes in outside temperatures and humidity throughout the year and result in changes in the equilibrium moisture of the grain. Operators must constantly monitor grain condition, particularly during periods of temperature change (fall or spring), to determine how temperature differences are effecting moisture migration in the bin. Aeration can be used to equalize grain temperature and moisture throughout the bin.
- Use a grain thermometer to track grain temperature.
- Schedule regular grain sampling and monitoring.
- Aerate and turn hot spots when detected.