The 4×5 round bale is a common package in forage production, characterized by its dimensions of four feet wide by five feet in diameter. The question of how many of these bales fit onto a single acre does not have a static answer, as the final count is a dynamic figure based entirely on two primary variables: the total tons of hay produced on that acre and the average weight of each individual bale. Calculating a precise number requires converting the field’s total harvest into pounds and then dividing that figure by the average weight of the package.
Understanding Hay Yield Per Acre
The most significant factor influencing the bale count is the total tons of forage harvested from the field, known as the yield per acre. This yield is not constant and varies dramatically based on agricultural and environmental conditions. For instance, a well-managed field of alfalfa might produce between 3.5 and 7 tons per acre annually. In contrast, a mixed grass hayfield, such as one with Timothy or Bermuda grass, yields a lighter tonnage, often ranging from 2 to 4 tons per acre.
The total biomass produced is heavily influenced by the soil’s composition and the grower’s management practices. Hay production thrives on fertile soil with balanced nutrients like nitrogen, phosphorus, and potassium. Favorable weather, including adequate rainfall or timely irrigation, is another major determinant of a high yield. The length of the growing season and the decision on how many times to cut the field throughout the year also directly impact the final cumulative tons harvested.
Defining the Weight of a 4×5 Bale
While the dimensions of the 4×5 bale are fixed at 4 feet wide and 5 feet high, the material packed inside causes its weight to fluctuate widely. The weight range for a standard 4×5 round bale is typically between 800 and 1,200 pounds, though extremely dense bales can reach 1,300 pounds. This variation is primarily due to the density of the packed material, which is controlled by the baler’s settings and the physical characteristics of the hay.
The operator’s setting for the baler’s tension or hydraulic pressure directly determines how tightly the forage is compressed. A higher pressure setting results in a more compact, heavier bale of the same size. The type of forage also plays a role, as dense, leafy alfalfa packs more weight into the fixed volume than lighter, stemmier grass or straw. The moisture content of the hay at the time of baling also contributes to the weight. Hay baled at a higher acceptable moisture level will be heavier than dry hay, though excessive moisture introduces risks of spoilage and spontaneous heating.
Calculating the Bales Per Acre
The most reliable way to determine the number of bales per acre is to use a direct calculation that merges the field’s measured yield with the average weight of the finished product. The formula is: (Yield per Acre in Tons multiplied by 2,000) divided by Average Bale Weight in Pounds. The 2,000 factor converts the yield figure from US tons into total pounds of hay.
For example, if a field produces 4 tons of hay per acre and the bales average 1,000 pounds each, the calculation is (4 tons multiplied by 2,000) divided by 1,000, resulting in 8 bales per acre. A lighter average bale weight of 800 pounds from the same 4-ton yield would increase the count to 10 bales per acre. Using an actual measured weight from a scale for a sample of bales, rather than relying on manufacturer estimates, provides the most accurate calculation.
Practical Adjustments for Field Loss and Storage
The theoretical calculation provides an important baseline, but it does not account for unavoidable material losses that occur during the harvesting process. Forage is lost at several stages, including during raking, where leaves can shatter, and during the baling process itself. These field losses are highly variable but can range from 10 to 25 percent of the total dry matter available, with an average loss around 15 percent.
After baling, further dry matter loss occurs during storage, which impacts the final marketable inventory. For large round bales stored outside and uncovered, losses due to weathering and contact with the moist ground can range from 5 to over 35 percent. The outer layer of a 4×5 bale contains a significant portion of the total volume and is susceptible to damage from rain and sun exposure. Producers must apply a percentage adjustment to their theoretical count to accurately estimate their final inventory.