Think that's the point the posters are trying to make.

Yes another $5 of fertilizer can be applied. And,, if $7 dollars of Nitrogen leaches out of the plant zone and is not available to the plant, there's not a whole lot of economic benefit.

"Here" agrotain is used so Nitrogen can be applied during the slow times, (like Feburary) and have the nitrogen held there in the root zone.  Which allow them to space out the work load and not be running day and night trying to get all the spring work done/crops planted / fertilized/sprayed/ etc.

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