Certainly interesting, much old information is based on supplying excess P because it is difficult to supply toxic levels and in field soil P gets immobilized over time and only a single application for one or two years. This study seems to be centered on ornamental and bedding plants for retail and where plants have fertilizer applied with every irrigation. A situation where the grower is not concerned with growth effects after sale. Also was P the only element concentration changed? I would guess with the growth plateau other nutrients became limiting factors. Most hydroponic formulas where concern is for high yields seem to use 30-60ppm, even in drain to waste and sometimes higher in recirculating. I recall some agronomic studies that show nutrient deficiencies suffered at early growth stages, even if corrected promptly, can have measurable impact on final yields, So maybe Hydro formulas use a bit extra for that reason.
6 inch pot have around 1.5 kg of soil, that is 0.001500 ppm if I go for 6 ppm of P, will it be 0.0015 x 6 = 0.009 ppm = 9 ug (micro grams) ?
Can you do a detail experiment on other macronutrients like Nitrogen (Ammonical, Nitrate) and Potassium?
Certainly interesting, much old information is based on supplying excess P because it is difficult to supply toxic levels and in field soil P gets immobilized over time and only a single application for one or two years.
This study seems to be centered on ornamental and bedding plants for retail and where plants have fertilizer applied with every irrigation. A situation where the grower is not concerned with growth effects after sale. Also was P the only element concentration changed? I would guess with the growth plateau other nutrients became limiting factors.
Most hydroponic formulas where concern is for high yields seem to use 30-60ppm, even in drain to waste and sometimes higher in recirculating.
I recall some agronomic studies that show nutrient deficiencies suffered at early growth stages, even if corrected promptly, can have measurable impact on final yields, So maybe Hydro formulas use a bit extra for that reason.
ah you have 3 other webinar vids on P you should link them in the description ua-cam.com/video/2f2A79m-jYk/v-deo.html
What would be a perfect ppm of nitrogen, phosphorus and potassium for peak growth and quiality for cannabis...
James Lincoln the plant will tell you..
Oh and by the way phosphorous pentoxide is not phosphate, it is just an antiquated arbitrary measure mandated by the government.