Many liquid fertilizers give instructions of achieving various Parts Per Million quantities. More commonly used for liquid injection fertilization systems. The amount of fertilizer is so small that including it in every watering is safe. In production systems some plants prefer this constant system as opposed to less frequent larger doses. Tim Chapman > > "From this study it was concluded that preferred conditions for both > species were fertigation of twice a week using fertilizer rate of 150 > ppm N under full sun" > > This is in reference to both Habranthus and Zephyranthes. What does 150 > ppm N mean? I know that would be nitrogen, but how would one know that > quantity? > >