Question about Phosphorus and Sulphur Concentration
A lot of commercial blends pretend to have a high phsophorus concentration for a bloom stage, about 90 ppm or more.
Some people say that in a bloom stage the plant need more phosphorus.
But according to most sources the normal phosphorus concentration is between 30 - 40 ppm of phosphorus. A cocopeat recipe says 37 ppm is enough including in the "bloom stage".
How much phosphorus a tomato plant need in the bloom stage? Is really necesary to rise the phosphorus? Or is just a marketing trick?
For a bell pepper how much phosphorus is necessary?
What is the maximum sulphur concentration? Where the tocixity begins?
Last question (sorry):
When we prepare nutrient solution of 40 ppm of phosphorus, this is the "initial concentration", right? Because if we change the nutrient solution every two weeks, when the first week has past, then the phosphorus concentration could be 20 ppm, because the plants are consuming nutrients. I can�t measure the phosphorus concentration, only the total dissolved solids and electrical conductivity. So, I can�t guess how much phosphorus I need to add to mantain the 40 ppm of phosphorus.
Thanks in advance.