It has been frequently noted that there seems to be quite marked differences in the requirements of plants for various elements. In fact requirements have appeared to be so divergent for some elements that crops have been divided into groups having high and low requirements, vi;:;., calcifuges, low lime, and calcifuces high lime. Groupings have also been made with regard to the nitrogen, phosphorus, and potassium requirements of plants.It has been noted by several investigators (2, 3, 6, 7 ) 3 , that plants will take up more potassium than is apparently required for normal growth. Just how prevalent this ability is in crops is not known.The investigation reported in this paper was started in order (a) to secure additional information on the so-called luxury feeding of plants on potassium and (b) to determine the significance of the luxury feeding in plant nutrition.. The work reported in this paper was done in conjunction with some other studies. which were made to determine the relationship of potassium to various functions of the plant. The experiments were conducted in the greenhouse and in the field. In the greenhouse, soil, sand, and solution cultures were used for the various crops. In all cases, unless otherwise noted, an abundant supply of all the plant food constituents excepting potassium was added to the cultures. Thus potassium was the only constituent which should have determined the amount of growth which was made. An optimum moisture content of the· soil and sand cultures was maintained as nearly as possible. In the field plats the fertilizers were broadcast uniformly by hand shortly before planting and worked into the soil by the seeding operations. The soil has been classified as a Clarksville silt loam by the U. S. Soil Survey and is supposed to be rather well supplied with total potassium.The crops grown were alfalfa, Hubam clover, cowpeas~ soybeans, oats, wheat, Sudan grass, corn, and cotton. The crops were sampled at different stages of growth. When only one sample was taken, it was secured when the crop was beginning to blossom. When several samples were taken, the first one was secured in the early stages of growth and the second when the plant was in blossom.'Contribution from the Department of Agronomy, Arkansas Agricultural Experiment Station, Fayetteville, Ark Published with the approval of the
