4fcb4a28_Quick_Guide_to_Plant_Nutrition__Signs_of_Deficiency
[Primary Nutrients] Potassium (K) [Function in Plant] Controls opening and closing of stomata; allows efficient use of water; stabilizes plant pH; prevents heat stress and drought damage [Sources for Fertilizer] Greensand Manure Wood ash Seaweed [Signs of Deficiency] 
Chlorosis (yellowing between veins in leaves); brown or dry leaf tips; yellow, brown, or purple spots in leaves; sickly overall appearance
A Quick Guide to Plant Nutrition
Signs of Deficiency