Hay baling preserves forage by removing moisture to halt microbial activity and prevent spoilage. After cutting, hay undergoes a natural curing process, dropping its initial moisture content, which can be as high as 75-80%. Determining the exact moment the hay is sufficiently dry to be compressed into bales is crucial for a successful harvest. Baling too early or too late compromises the nutritional value and safety of the stored feed. Accurately assessing the moisture content is the most important decision a producer makes.
Defining Safe Moisture Levels for Baling
Safe moisture content for storage varies based on the size and density of the finished bale. Denser bales require a lower moisture percentage because they have less internal air circulation, which helps prevent spontaneous heating. Small square bales, the least dense, can tolerate the highest moisture levels, generally 18% to 20% without preservatives.
Large round bales are safest when moisture content is between 15% and 18%. High-density large square bales should be baled at the lowest range, ideally 12% to 16%. Legume hays, such as alfalfa, are prone to leaf shatter if allowed to dry too much. Achieving these goals requires reliable testing methods that gauge the internal water content of the plant material.
Practical Field Tests for Moisture Estimation
Producers rely on simple, tactile methods to estimate hay moisture content before using instrumentation. The “twist test” is a common technique that provides a rough measure of stem dryness. To perform this, gather a handful of hay from the windrow and twist it tightly, similar to wringing out a cloth. If the hay is sufficiently cured, the stems will snap or break cleanly under the twisting force. If the stems bend without breaking, or if moisture is visibly expressed, the hay is still too wet to bale safely. This test is useful for assessing the slow-drying stems, which hold moisture longer than the leaves.
The “feel and sound” test focuses on the leaves and texture. Hay dry enough to bale feels crisp and brittle to the touch. When a sample is vigorously shaken or compressed, it should produce a distinct rustling or shattering sound, indicating dry leaves. If the hay feels pliable or soft, too much moisture remains, and baling should be delayed. Experienced operators use these sensory cues to make a preliminary determination.
Using Electronic Moisture Meters for Accuracy
Electronic moisture meters offer a precise numerical reading, which is essential for making the final baling decision. The two main types are handheld probe meters and baler-mounted continuous monitoring systems. Handheld probe meters require the operator to insert a long probe deep into a formed bale or into a tightly packed sample of windrow hay.
To test loose hay, the material must be tightly compressed into a container, such as a five-gallon bucket, to simulate bale density. This compression is necessary because the meter’s reading is based on electrical resistance, which is highly dependent on density. For a reliable reading, multiple samples (often 10 to 20) must be taken from various locations and averaged.
Continuous monitoring systems are installed directly onto the baler, providing real-time moisture readings from sensor pads inside the bale chamber. These systems allow the operator to adjust speed or stop baling immediately if the moisture content exceeds the safe threshold. All electronic meters must be periodically calibrated, sometimes by using a microwave oven to fully dry a hay sample and compare the meter’s reading to the true moisture content.
Consequences of Improper Moisture Content
Baling hay with incorrect moisture content results in significant losses, both economic and in feed quality. When hay is baled too wet (typically above 20% moisture), the trapped moisture encourages the rapid growth of microorganisms like bacteria and mold. This microbial activity generates heat, which can denature proteins, reducing the hay’s nutritional value and palatability for livestock.
The most severe consequence of baling wet hay is the risk of spontaneous combustion. This occurs when the internal temperature of the bale exceeds 175 degrees Fahrenheit due to sustained microbial respiration and subsequent chemical reactions within the tightly packed mass. Conversely, baling hay that is too dry (often below 12% moisture) causes excessive leaf shatter during the raking and baling process. Since the leaves contain the majority of the hay’s protein and nutrients, this shattering significantly reduces the overall feed quality.