Environmental Conditions Affect Time To Safe Hay Baling

Environmental conditions that exist when forages are ready to be harvested influences the amount of hours that it takes to get to a safe baling moisture. A growing forage will have 75 to 80 percent moisture. A moisture content of 20 percent is considered a safe baling moisture for small rectangular bales and will be slightly less for large round bales and large rectangular bales. The following tables are from the Purdue Forage Field Guide (Purdue publication ID-317) and provide useful information regarding the effects temperature, relative humidity, and soil moisture condition have on the time it takes from cutting to baling. When relative humidity is 90 percent, cut hay will never get to a safe baling moisture content of less than 20 percent moisture regardless of temperature (Table 1). With a relative humidity of 70 percent or less, the higher the temperature the lower the predicted moisture will be for hay in storage, although a 70oF temperature at 70 percent relative humidity will not achieve a safe baling or storage moisture level.

Effects of soil moisture condition and solar radiation on the number of hours to achieve 20 percent moisture alfalfa are found in Table 2. This research indicates that the number of hours when conditions are cloudy with wet soil moisture are approximately three times longer than when sunny and dry soil conditions occur.

It is critical that environmental conditions be considered when making dry hay. Haymaking conditions are likely to never be the same within a harvest season.

 Table 1. Predicted Final Moisture Content of Baled Hay

Relative Humidity (%)
Temperature (oF) 30 50 70 90
70 10 13 21 39
80 8 12 20 38
85 7 10 18 37
95 5 8 18 36


Table 2. Predicted Hours to Dry Alfalfa from 80% to 20% Moisture

Air Temperature (oF)
Sun1 Soil Condition2 50 60 70 80 90
Cloudy Wet 44 41 38 35 33
Cloudy Dry 36 34 31 29 27
Sunny Wet 16 16 15 15 15
Sunny Dry 14 13 13 12 12
1Cloudy = 100 Btu/hr-ft2 solar radiation. Sunny = 280 Btu/hr-ft2 solar radiation.
2Wet soil = 20% moisture content. Dry soil = 9% moisture content.
Source: Silage and Hay Preservation (Natural Resource, Agriculture, and Engineering Service publication NRAES-5)


Raking hay into a windrow before baling occurs. (Photo Credit: Keith Johnson)

Raking hay into a windrow before baling occurs. (Photo Credit: Keith Johnson)

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