Easy Tool to Determine Total Dry Matter Pounds/Acre

Many producers are finding the STAC Forage Assessment a valuable tool to determine Animal Days per Acre (ADA), but what if you are wanting to determine pounds of dry matter available or even total dry matter per acre? With a little more additional math, you can get that answer to help you determine gross profit potential for hayfields or for other uses. Here’s a little more information about how to do that from HMI Certified Educator and Grazing Naturally Consultant Dick Richardson of Australia.

 As noted on HMI’s STAC Forage Assessment worksheet, the SDA/ADA calculations are as follows:

STAC ADA in acres

• Sole = 12 ADA

• Toe = 24 ADA

• Ankle = 36 ADA

• Calf = 48 ADA

• Thigh = 60 ADA

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If you want to know how that translates to pounds of dry matter per acre or hectare for grazing, you use the correction factor of 24.75/acre or 12.25/ha.

So, in the case of pounds/acre the pound reading would be:

• Sole = 300 pounds/acre

• Toe = 600 pounds/acre

• Ankle = 900 pounds/acre

• Calf = 1,200 pounds/acre

• Thigh = 1,800 pounds/acre

For example, a STAC reading averaging 50 will give you 1,237.5 pounds per acre of forage to graze with adequate residual left over.

To convert that number to total dry matter/acre you would multiply the pounds/acre by 4. Using the example above, you would multiply 1,237.5 X 4 to get 4,950 pounds total dry matter per acre.

Dick further notes that “Good hay, cut early, i.e., not in a reproductive state, can be cut really short and responds back beautifully while still building soil. In this case, use the STAC method for pounds/acre and multiply the outcome by 4. This is true for a mature cereal hay cut short as well. If it is mature hay, (hay that rips nutrients from the soil and is cut at 4 inches to try and keep it alive), then you would only multiply the outcome by 3. The Grazing Naturally STAC method only calculates what stock can actually eat out of a paddock. Total Dry Matter is about 4 times the STAC figure dependent on biome. Take a look at my website naturesequity.com.au to see how it works. It’s on the free training list.”

Download your STAC Forage Assessment Worksheet here.