Oats are a widely cultivated cereal crop, valued globally for their nutritional profile and versatility in both human and animal consumption. The successful transition of this grain from a standing field crop to a usable, storable product requires careful attention to timing and processing techniques. Understanding the steps involved in oat harvest, from the initial cut to final storage, ensures the preservation of grain quality and maximum yield. This guide breaks down the methods needed to convert the mature oat plant into a clean, shelf-stable grain.
Determining Optimal Harvest Time
The timing of the oat harvest significantly impacts the final quality of the grain. Visual inspection provides the first cue, as the oat fields transition from green to a golden-yellow or cream color, signaling that the plant is nearing physiological maturity. Farmers rely on the “hard dough stage” of the kernel as a physical benchmark for optimal cutting, which corresponds to a grain moisture content below 30%. At this stage, pressing a thumbnail into the kernel should leave a distinct dent without expressing any milky liquid.
Harvesting too early, when moisture is too high, risks poor test weights and low milling quality. Waiting too long increases the chance of grain shattering and loss due to weathering.
For growers planning to use the straight-combining method, the grain must dry naturally on the stalk until the moisture level reaches approximately 14 to 15%. Conversely, if the crop is destined for swathing, the ideal time to cut is earlier, when the moisture content is higher, often between 20 and 25%. This slightly earlier cut allows the crop to cure in the field while minimizing the risk of pre-harvest loss.
Harvesting Methods: Cutting and Gathering
The physical removal of the oat crop from the field is executed using two primary strategies, depending on the scale of the operation and the desired moisture level at cutting. Large-scale farming often utilizes the method of straight combining, where a mechanical harvester cuts the standing grain and simultaneously separates the kernel from the plant material. This method is most effective when the crop is uniformly mature and has dried down naturally to the final harvest moisture content in the field.
A different approach is swathing, which involves a specialized machine cutting the oat stalks and laying them down in neat rows called windrows. Swathing is performed at a higher kernel moisture content, allowing the cut plants to finish drying and undergo a natural curing process in the field. The combine harvester then returns days later to pick up the dried windrows, which minimizes shattering losses compared to leaving the grain standing in adverse weather.
For small-scale or homestead operations, the initial cutting and gathering is often done manually using a sickle or scythe. Once cut, the stalks are typically tied into bundles, or sheaves, and propped up in the field to dry. This mimics the field-curing action of a swathed windrow and ensures the grain heads are completely dry before the next stage of processing begins.
Post-Harvest Processing: Drying and Threshing
Immediately following the cut, the harvested oats, whether in windrows or sheaves, must be sufficiently cured before the grain can be separated from the straw. This curing period, sometimes referred to as field drying or “sweating,” is necessary to bring the moisture content down to a level that permits clean separation. If the grain was straight-combined, the drying process occurs within the combine, but the kernels still need to be managed for safe storage.
Threshing
The act of threshing is the physical process of liberating the grain kernel from the surrounding seed head and stalk material. In large operations, the combine harvester handles this by beating the cut material against a concave surface with a cylinder or rotor. Small-scale threshing can be achieved by placing the dried oat heads inside a clean container, such as a metal drum or bucket, and beating them with a stick or flail to knock the kernels loose.
Winnowing
Once the kernels are separated, the resulting mixture of grain, broken straw, and chaff must be cleaned through a process called winnowing. Winnowing leverages the difference in weight between the heavy grain and the light chaff to achieve separation. This is commonly done by pouring the threshed material from one container to another in front of a steady airflow, such as a fan or a natural breeze. The lighter chaff is blown away by the air current, while the heavier, cleaned kernels drop directly into the lower container.
Preparing Oats for Long-Term Storage
After the grain has been threshed and winnowed, the final step before storage is ensuring the moisture content is low enough to prevent spoilage. For the grain to remain stable over a long period, its moisture content must be reduced below a level that supports the growth of mold and mildew. The standard for safe, long-term storage of oats is typically a moisture content between 11% and 13.5%.
Storing grain above this level, such as at 15% moisture, requires continuous aeration to prevent the development of hot spots and fermentation. For commercial quantities, aeration fans are often used in storage bins to circulate cool, dry air and gently reduce the grain’s moisture to the desired specification. Regardless of the scale, the cleaned oat kernels should be placed in a cool, dry, and clean container, which will minimize the risk of pest infestation and quality degradation.