It is difficult to diagnose a soluble salts problem by symptoms alone. Often nutrient deficiencies and root diseases cause the same symptoms. Therefore a soil test is advisable. A UMass soil test reading of 100 or greater is excessive during the early stages of growth is a cause for concern. Trace element toxicities.
Symptoms appear as numerous small dark spots and mottling of the foliage.
Toxicity can be avoided by keeping the pH in the range of 6.0-6.8 for susceptible crops and through the use of fertilizers with lower trace element levels. Pansy, petunia, tomato, eggplant, and pepper are most sensitive to ammonium nitrogen, but many other bedding plants can be harmed if ammonium becomes excessive. 17.0 y One application every 7-10 days. Fertilizer Rates Use 50-100 ppm N prior to transplanting from the flat or plug tray. Potassium nitrate is best for this purpose.