27 COLLIER SPORTS © ‘ Gras Guy ’ Understanding Weight/Weight (W/W) and Weight/Volume (W/V) Water Fertiliser 25:0:0 (w/w) Water Fertiliser 33:0:0 (w/v) Following the implementation of 2019/1009 EU Fertilising Products Regulation (FPR) the way some manufacturers will calculate the nutrient content of their liquid fertilisers is changing. This is important because it affects the way you calculate the amount of nutrient being applied. IMPORTANT: the products are not changing, just the way the nutrient content is shown. EXPLANATION: There are three possible methods for displaying the nutrient content of a liquid fertiliser…. • Weight/Weight (w/w) weight of nutrient per weight of liquid, • Weight/Volume (w/v) weight of nutrient per volume of liquid • Volume/Volume (v/v) volume of nutrient per volume of liquid (not commonly used) To conform to the FPR regs some manufacturers will change from a w/w method to a w/v method. Use the following formula to calculate nutrient input: Nutrient content / 100 x Application rate = kg nutrient/ha. Example: An application Greenmaster Liquid High N (33-0-0) at 80L/ha would deliver…. Nutrient content / 100 x Application rate = kg nutrient/ha. (33/100) x 80 = 26.4 kg/ha N applied Liquid Fertiliser (Weight/Volume) For example: Greenmaster Liquid High N 25:0:0 + 2 % MgO + TE (w/w) ...will change to... Greenmaster Liquid High N 33:0:0 + 2.6 % MgO + TE (w/v) This makes the calculation of nutrient applied a lot simpler because the specific gravity is no longer needed.
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