Nutritional Deficiency Symptoms in Cotton

BOTANICALLY cotton is a perennial plant, but it is grown as an annual crop in the main cottonproducing sections of this country. The plant has an indefinite growth period and is considered a long growing season crop. These conditions make it possible to study the appearance and the extent of the deficiency symptoms over a long growing season. Before describing the deficiency symptoms associated with the various nutrients it is desirable to have a general statement concerning the soil and climatic conditions which may be related to the appearance and extent of the deficiency symptoms. Certain nutrient deficiency symptoms such as potash and possibly sulphur are most likely to occur during relatively dry growing seasons; whereas magnesium and nitrogen deficiency symptoms are more frequent during relatively wet growing seasons. Important potassium and sulfur compounds in the soil are only slightly soluble in the soil solution, and there may not be sufficient amounts of these nutrients available during dry growing seasons. Magnesium and manganese deficiency symptoms are most likely to occur during relatively wet growing seasons, particularly where large amounts of nitrates, sulfates, or chlorides are added to the soil in fertilizers. Magnesium nitrate, sulfate, and chloride are highly soluble in water and may be readily leached from the soil. The data in Table I show the percentage of red leaves of cotton plants indicating magnesium deficiency in cotton where various forms of nitrogen are