Barley is a major cereal grain used globally for livestock feed, malting for brewing, and various food products. A successful harvest requires accurate timing and meticulous execution, as the quality of the final product is directly tied to the process from the field to the storage bin. Proper harvest management minimizes grain loss, reduces the risk of spoilage, and ensures the barley meets specific quality standards, such as the high germination rates necessary for malting. Understanding the stages of maturity and the necessary post-harvest steps maximizes both yield and market value.
Determining Optimal Maturity
Identifying the precise moment the barley is ready for harvest is the most important decision, balancing maximum dry weight with the risk of field loss. Physiological maturity, the point of maximum kernel dry weight, occurs when the stem just below the head (the peduncle) loses its green color and turns light yellow. At this stage, the kernels still hold a relatively high moisture content, typically ranging between 25 and 30 percent.
Harvest maturity occurs later, after the grain has naturally dried down in the field to a moisture level suitable for combining and storage. A key visual cue for this stage is the gradual nodding of the barley heads as they lose moisture and become heavier. When the heads have completely fallen over, the grain is near its lowest possible field moisture, which can be 13 percent or less in dry conditions.
The ideal moisture content for harvesting is 14 to 15 percent, balancing harvesting efficiency with minimizing field losses. For safe long-term storage, the moisture content must be 12.5 percent or less to prevent mold and spoilage. A hard kernel that cracks when bitten indicates the grain is approaching the hard-dough stage, signifying a moisture content around 30 percent, which is the earliest safe point for pre-harvest management.
Pre-Harvest Preparation
Before any machinery enters the field, a decision must be made regarding the harvest method: direct combining or swathing. Direct combining, or straight-cutting, is the preferred method for malting barley, involving harvesting the standing crop in a single pass. This method reduces the risk of pre-harvest sprouting and staining, especially in wet conditions, because the heads remain elevated off the ground.
Swathing involves cutting the crop and laying it into windrows to dry further before a combine with a specialized pickup header collects it. This strategy is used when the crop has uneven maturity or when a faster dry-down is needed due to weather concerns or to manage late-season weed growth. If swathing, timing is crucial; it should be delayed until the kernel moisture is below 30 percent, ensuring the grain has finished filling before cutting.
Regardless of the chosen method, all harvesting equipment must be thoroughly inspected and calibrated beforehand. Combine components, including the header, feeder house, and sieves, should be checked for wear and proper alignment to ensure a smooth, uniform material flow. Field obstacles, such as large rocks or old equipment, must be cleared from the path to prevent machinery damage and maintain a consistent harvesting speed.
Methods of Cutting and Threshing
The core of the harvest operation is the combine harvester, which performs the three primary functions of cutting, threshing, and cleaning the grain. For barley, the goal is to detach the kernel from the head while minimizing kernel damage like cracking or skinning, which is important for malting varieties. Grain damage is caused by excessive cylinder or rotor speed, so this setting should be kept as low as possible while still achieving complete threshing.
Internal settings require balancing the concave clearance and the cylinder speed. The concave clearance should be tightened first to ensure the grain is adequately threshed, and then the cylinder or rotor speed can be adjusted for fine-tuning. For barley, a rotor speed of 700 to 850 RPM, combined with a tight concave clearance, is recommended to prevent unthreshed kernels, or “white caps,” without causing excessive breakage.
The cleaning shoe must be carefully adjusted to separate the threshed grain from the chaff and straw. Fan speed and sieve openings work in tandem; the fan speed must be high enough to “float out” the lighter material without blowing grain out the back of the machine. Typical fan speeds for barley range from 850 to 1100 RPM, and the chaffer and sieve openings should allow clean grain to pass through while directing larger debris back into the tailings for re-threshing.
Post-Harvest Drying and Storage
Once the grain leaves the combine, the focus shifts to rapidly reducing the moisture content to a safe level for storage. Barley should be dried down to 12.5 percent moisture or less to prevent mold growth and the degradation of quality. Harvesting the grain slightly tough, at 14 to 15 percent moisture, necessitates immediate drying to meet the long-term storage standard.
Drying is accomplished using aeration, where fans push ambient or slightly heated air through the grain bulk in the storage bin. Natural air drying requires favorable conditions: air temperatures above \(50^\circ\)F (\(10^\circ\)C) and a relative humidity below 60 percent, with an airflow rate of at least 1 cubic foot per minute per bushel. If the grain is high-moisture or contains green kernels, aeration must be initiated immediately and maintained until the moisture front has moved completely through the grain.
Temperature monitoring within the storage structure is important because warm grain holds its heat, promoting insect development and fungal growth. Aeration cooling aims to maintain a consistent temperature, ideally between 50 and \(59^\circ\)F (\(10\) and \(15^\circ\)C), throughout the grain mass to slow biological activity. Cleaning the grain prior to storage removes foreign material, such as straw pieces and broken kernels, which significantly reduces the risk of spoilage and improves the overall test weight.