Fertilizer stock solution

[joe_orch]

I am making a stock solution of 20-20-20 to make 32 gallons of working solution. I am shooting for 125ppm N. The formulas state I should use .48 tsp. of fertilizer to make 1 gallon of working solution. I figured to multiply .48 x 32 for the stock solution, which figures to 5.12 tablespoons to 1 gallon for the stock solution, which I also added 5.12 TBSP of Pro-tekt. to get the working solution to a ph of 6.5. I use 4 oz. of stock to 124 oz. of RO water to get my working solution. When I test my working solution the tds reading is 181 ppm total which seems low to me. Am I figuring this right? My TDS meter is calibrated to the proper TDS reading of 1382.

Thanks for the information,

Joe

[Ray]

At 125 ppm N, your stock solution should have around 288 ppm from the N, P, & K alone.

I can think of three simple possibilities: 1) That TDS meter is not calibrated correctly (it really takes ate least 2 data points to establish the correct calibration curve), 2) by adding Pro-Tekt to your stock solution, you have precipitated come of the fertilizer constituents (Pro-Tekt and fertilizer should not be mixed until they are in their final dilution), or 3) both.

You might want to read this: TDS and EC

[joe_orch]

Ray, Thanks for the info. I am thinking my TDS meter is on the fritz. I tried .5 tsp. DG 7-9-5 per gal. of RO and got a reading of 224ppm with no other additives, and then tried .5 tsp. 20-20-20 per gal. RO with no other additives, and got a reading of 160ppm. Very strange

Thanks,
Joe