Excessive nitrogen reduces the severity of both physiologic leaf spot and tan spot, but increases Septoria leaf blotch incidence. Avoidance of excessive nitrogen fertilizers can reduce Septoria leaf blotch damage. When physiologic leaf spot occurs on leaves in the upper plant canopy, the field appears drought stressed. Damage due to physiologic leaf spot typically is minor, but damage has been moderate to severe since 1989. It is possible that chloride may affect physiological processes such as water relations, photosynthesis, or kernel development to minimize damage caused by physiologic leaf spot.
Chloride is important in photosynthesis and osmotic relations of guard cells in leaves.
Chloride apparently affects a wide range of developmental processes, including rate of spikelet formation, and maturation, and volume and weight of kernels. Chloride fertilizers may increase grain yields by prolonging photosynthetic activity. Calcium is an essential nutrient in plants that protects the roots from low pH, toxic ions, salinity, and ion imbalance. Calcium delays senescence and reduces membrane damage and leakiness. Calcium deficiency has been associated with reduced cold hardiness, increased risk of magnesium toxicity, and reduced growth of meristem tissues.