Active Ingredient Rate

Labels regulate the active ingredient, not the product. The maximum seasonal rate, the pre-harvest interval and the resistance-management guidance are all written against grams of active per hectare, and the product is merely the vehicle that carries it. Whenever two products contain the same active — which is the normal situation once a patent expires — this conversion is the only way to compare them.

Liquid formulations state their strength as grams of active per litre, and the number is usually in the trade name: "glyphosate 360" is 360 g/L, "480" is 480 g/L. So 2.5 L/ha of a 360 formulation delivers 900 g a.i./ha, and 1.875 L/ha of the 480 delivers exactly the same. Those are equivalent applications at different product rates, and a grower switching between them who keeps the product rate the same has changed the dose by a third.

Two traps sit close by. Dry formulations state strength as a percentage by weight rather than grams per litre — a 75% WG at 1.0 kg/ha delivers 750 g a.i./ha — so the arithmetic is the same shape but the units differ. And some actives are sold as salts or esters, where the label may state either the acid equivalent or the salt. Glyphosate is the notorious case: the same jug can be honestly described as 540 g/L of potassium salt or 450 g/L acid equivalent. Resistance-management limits are written in acid equivalent, so comparing a salt figure against an a.e. limit understates the dose by 20%.