Nutrient Balance in Corn Growing in Southern States as Revealed by Purdue Plant Tissue Tests 1

C yields are aenerally low in the southern sta~es, even in fertility plots supposedly well fertilized. In order to study the relative causes of these low corn yields a cooperative plan between fhe Alabama, Georgia, and Mississippi aEricultural experiment stations and the National Fertilizer Association was formulated whereby the status of the plant nutrients in the corn plants in these experimental plots could be determined by means of the plant tissue test technic developed at Purdue University. The Purdue test (~)a is used in making determinations for nitrates, phosphorus, and potassium. These tests are semi-quantitative and the relationship of the balances between the nutrients must be considered in interpreting the tests (~). The nitrate level in the corn plant is determined by splitting the stalk and applying drops of a solution of diphenylamine in sulfuric acid along the exposed tissue. The presence of nitrates is denoted by the blue color developed; the more intense the color, the higher the nitrate supply in the conducting tissue. Phosphorus tests are made on the finely cut tissue from the new leaf growth, before tasseling and later from the base of the tassel. The tissue is shaken in a vial with a dilute solution of KC1 and ~he molybdate-s~annous chloride test for phosphorus is made. The phosphorus supply is indicated by the intensity of the blue color developed.