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What is an Acre in Terms of Fumigant Rates?

What is an acre? More specifically, what is an acre when we speak of soil fumigants? No other topic has caused more confusion and misapplication than the understanding of what constitutes an acre for fumigation purposes. An acre is defined as 43,560 square feet. Some try to define an acre in terms of plastic mulch acres, row acres or real estate acres, but in reality there is only one definition of acre that can be applied universally to all situations and that is the treated acre. To speak in terms of the treated acre means that you have eliminated all potential variables and you now have a standardized term. An acre is defined by that area which is actually treated with fumigant. In the case of bedded, mulched crops a treated acre only deals with the soil in the bed and ignores the row spacing which can vary from farm to farm and is not a treated area. If a bed is 28 inches wide, then it does not matter whether the beds are spaced 5, 6, 6.5 or even 7 or more feet apart.

If you are talking about broadcast fumigation, then you already are talking about the treated acre because all of the area is treated. This has resulted in some folks trying to refer to "broadcast equivalent rates" when dealing with bedded soil. The idea is to try and express the rate as what it would be if you took the rate you used in the bed and then spread it out over the entire acre. This would allow one to use 400 lbs. of fumigant per treated acre in a bed and claim that they were only using 200 lbs. per broadcast equivalent acre. This is nonsense. The rate is the amount you apply per acre and the acre has been defined for centuries as 43,560 square feet. You are talking about the area you treated, plain and simple. No smoke, no mirrors, no equivalency. In order for a "broadcast equivalent rate" to meet the definition of equivalent, it would have to be based on the treated area being equal, otherwise, by definition, they are not equivalent. Your 400 lbs./acre will only treat 1 acre. It may be an acre all in one spot as a broadcast application or it may be 14,520 ft of 3 ft wide bed applied to the bed itself, but whichever way you go, it is still 400 lbs./treated acre.

Some individuals want to factor in the row spacing by stating that their acre consists of 3 rows of bed that are 7260 ft in total length (3 rows x 2420 ft each). But does it really? No. It is a convenient term for growers to use in order to express their production or even to somewhat standardize fertilizer rates, but the reality is that they are counting the bed and the row middles or wheel furrows in the process. If their beds are spaced 6 ft on centers, then they may truly be able to get 7260 linear feet of bed or row in each acre. But wait, if we are doing this fuzzy math, what about the ditches? Do we not count them? After all, we are counting the row middles; why not count the ditches, too? So if we counted the row middles and the ditches and there were 3 rows between ditches, what would we have? Assuming we have a 3 ft bed and the row middle is 3 ft wide on each side of the bed, and we have a ditch every 3 rows and that ditch is spaced 6 ft from the center of the outside bed to the center of the ditch, we would have 1.36 A instead of 1.0 A.

Using the above example, what would our rate be if we were trying to express it as a "broadcast equivalent"? We applied 400 lbs. to 1.36 acres, so our broadcast equivalent rate would be 293 lbs/broadcast equivalent acre. Now is that what we really did? No, we used 400 lbs. in the bed or 400 lbs./treated acre. How can that be equivalent to 293 lbs. per broadcast equivalent acre? Equivalent means equal, remember? So are they truly equal? No. If you had nutsedge in that field, you would know how unequal they are within 2 weeks. Some use the simplistic approach that since the bed is 3 ft wide and the beds are 6 ft apart, then you are treating half of each real estate acre; therefore, your broadcast equivalent rate is 200 lbs., but I already showed you it isn’t, didn’t I? Confused? I certainly hope so.

This is why the only logical expression of rate per acre is the actual rate per treated acre. Thus, an acre is truly an acre and everyone speaks the same language. Any other approach defies logic and good reasoning.

(James P. Gilreath, GCREC-Bradenton, Vegetarian 04-06)