Phosphorus

Chemical symbol: P One of the three primary macronutrients, phosphorus is essential for healthy plant growth. It contributes to developing long roots for better access to other nutrients. Phosphorus also helps plants use energy for fruiting and flowering. Symptoms of phosphorus deficiency include slow or stunted growth and bluish leaves.

Potassium

Chemical symbol: K One of the three primary macronutrients, potassium helps plants grow strong cell walls, which in turn allows them to produce heavier yields. It also aids in efficient water use. Symptoms of potassium deficiency include weak growth and limp stems.