Harvesting and Storing Organic Grain
By: Dr. Ron Heiniger, Crop Science Extension Specialist, NCSU; Randy Weisz, Crop Science Extension Specialist, NCSU; Molly Hamilton, Crop Science Extension Assistant, NCSU
Harvesting and storing organic grain is a critical step in producing a high quality crop for sale. Organic grain crops are harvested with the
same type of equipment and techniques as conventional crops. If conventional crops are also harvested, the machines and hauling equipment (combines, augers, trucks, etc.) must be cleaned thoroughly between crops to prevent genetic and/or prohibited materials contamination and to maintain the value and identity of the organic crop. Also, if the harvesting, handling or storage equipment is not dedicated to organic, a maintenance log should be kept to show that the equipment was thoroughly cleaned of conventional grain before harvesting organic grain. Transgenic technology (i.e. Bt corn or Roundup Ready soybeans) that contaminates the organic grain may cause the grain to be rejected by the buyer if it tests positive for these crops. To prevent genetic (and pesticide) contamination of organic grains, it is also a good idea to harvest the outside rows first, especially those neighboring conventional crops, and treat them as conventional (harvest, store and sell as conventional grain). For more information on protecting the integrity of organic grains during harvest, see this article.
With organic grains, storage is often necessary as buyers cannot or will not buy a season’s grain at the time of harvest. Grain may need to be stored for a few months, or longer, until the buyer is ready and willing to take it. Often, prices for grain also increase in the months after harvest, making storage of organic grain even more worthwhile. Store organic grains at the proper moisture and temperature recommended for reducing disease and pest problems.
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 preventative post-harvest grain management approach is the SLAM system (Sanitize/Seal, Load, Aerate, Monitor).
Sanitize/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 all locations below the roof eaves.
Load
- 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% 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 most fines and small foreign matter.
- Spreading/Leveling grain – a level grain surface is easier to manage and less likely to change temperature during storage.
Aerate
- Maintain grain temperature – Grain temperature should be below 60 oF 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 oF 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 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.
Monitor
- Use a grain thermometer to track grain temperature
- Schedule regular grain sampling and monitoring
- Aeration/turning of hot spots when detected
Insect Management in Stored Organic Grain
The best way to manage for insect pests in stored organic grain is to avoid them. Keeping bins, ducts and augers clean, and grain stored at low temperature (≤60° F) and low humidity, is very important for preventing problems in the stored grain. Another suggested and often used method to prevent insect pest problems in stored wheat and corn is to add food-grade diatomaceous earth (DE) to the grain as it is being loaded into the storage bins (at a rate of up to 40 pounds per 1000 pounds of grain). 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. DE works because the surface of each particle 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. To identify insect pests of stored grain, see the 2004-05 NC Small Grain Production Guide or the NC Corn Production Guide.
Web Resources and Articles
Harvesting High-Quality Organic Grain - Small Grains, Corn, Soybeans (ACRES article - pdf file)
Protecting the integreity of organic grains during harvest (a New Farm article)
Is your farm safe? Protecting your crops from genetic contamination (ACRES article - pdf file)
Stored Grain Pest Management (ATTRA publication)
