Potassium supplements are recommended for root development. While plants are growing the amounts of potassium in the stems ranges from 4000 to 10,000 ppm. When the plant begins to mature this drops to about 3000 ppm. Signs of deficiency vary on various crops. Lettuce and cabbage show signs on tip edges that dry out and die, and overall size of plant is reduced.
Carrots show dry curled leaves.
Sweet potatoes form a long and thin tuber. Peas show dwarfed plants and seeds with a thick coat. Soybeans are wrinkled and misshapen. Potassium deficiency generally shows that the growing portions of plant are failing to grow. Potassium is found in highest concentrations in plant leaves, rather than seeds.