Found this resource from this link http://msucares.com/pubs/infosheets/is1668.pdf
By Dr. Alan Henn
Plants must have a proper growing medium for healthy growth. Most often the growing medium is soil. To support healthy plant growth, soil must have the moisture, structure, pH, mix of organic matter, and available nutrients to meet the plant’s needs. A fertile soil is a well-blended mix of these. When any of these components is damaged or falls out of correct proportion, plant growth is affected. Most common problems result from imbalances in nutritional elements or improper pH.
Susceptibility and incidence to grey mold and myrothecium incidence increase with increasing nitrogen in some greenhouse plants. On the other hand, Rust on perennial ryegrass is lower when plants are grown under high nitrogen fertilization. It is not just the amount of nitrogen that is important; its form is also important, either nitrate or ammonium. One disease (foliar, wilts, or root rots) may be made worse by ammonium nitrogen, but another may be made worse by nitrate nitrogen.
Nitrogen levels should be balanced with potassium, since disease susceptibility generally increases with higher nitrogen-to-potassium ratios. Some diseases that are made worse by too much nitrogen may at least be partially reduced by increasing potassium. This is true in grey mold in tomato and in some bacterial stem rot. Likewise, Melting out, Leaf spot, Pythium blight, and Sclerotina dollar spot are greater under high nitrogen fertility. This effect can be offset for all but Sclerotina dollar spot by increasing phosphorus and potassium levels, bringing the fertility level more in balance.
nutrient deficiencies in Mississippi
Nitrogen: Leaves are light green and lower leaves turn
yellow or light brown. Stems may be thin and shortened.
Phosphorus: Leaves have a purple tint or are bluish green.
Lower leaves may turn light brown. Stems may be thin
Potassium: Thin stems, which may die-back in severe
shortages. Older leaves may yellow, and the margins and
tips may brown.
Calcium: New leaves are distorted with curled margins.
They may have brown spotting.
Iron: Young leaves are yellow between the veins, but the
veins remain dark green. Sometimes brown spots appear.
By Dr. Alan Henn, Associate Extension Professor, Entomology and Plant Pathology
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Information Sheet 1668
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. VANCE H. WATSON, Director (POD rev-10-07)