Liebig's law shows that a plant's growth is limited by the nutrient in shortest supply. This means that any deficiency in the big three of Nitrogen, Potassium or Phosphorous will limit the plant’s growth when it uses up the least plentiful element.

Cultivating plants in soil requires higher phosphorus levels to offset clay colloidal particles that bind to phosphorous, and to offset soil microbes that compete for the remaining phosphorous. Pure Blend Pro Soil Bloom is specifically formulated (1.5-4-5 ) to provide additional phosphorus and nutrients for blooming, fruiting and flowering plants while also feeding microorganisms.
Cultivating fruiting and flowering plants in hydroponics requires less phosphorous levels than potassium and even nitrogen. In hydroponics, phosphorous levels that are too high tend to lock out calcium, magnesium and trace minerals. On the other hand, plants grown in soil need higher phosphorous levels due to clay colloidal particles that bind up phosphorous. Microbes in the soil also compete for the phosphorous.When cultivating fruiting and flowering plants in soil, growers usually need to double or triple phosphorous levels, unlike hydroponics, thus making the 1.5-4-5 formula ideal for soil applications.