Interrelationships of Calcium, Nitrogen, and Phosphorus in Vegetable Crops.

Coincident with the rapid advances being made in soil science, an increasing interest has been shown in the soil mechanisms as they control plant nutrition, growth, and crop production. One of the most influential factors involved is that of the interaction of nutrients. The equilibrium among ions in the soil and the culture solution has lately been designated as "nutrientelement balance. " Emphasis has been placed on the interrelations of essential plant nutrients, on "antagonisms" between specific cations, and on the possible application of such relationships to fertilizer practices in the field. In the nineteenth century WOLFF (37) noticed that with barley the greatest growth occurred in "complete" nutrient cultures. Excess potassium depressed yields. It was observed, however, that the depression in growth could be overcome by the addition of another nutrient. He noted also that sodium amendments offset the effects of excess potash. LAGATU and MAUME (16) recorded a decrease in the yield of grapes when potassium was omitted from an otherwise balanced fertilizer application. THOMAS (25, 26, 27) substantiated the work of LAGATU and MAUME, and his data further emphasized the importance of proper balance in fertilizer applications with reference to absorption. Associated with nutrient balance are the frequently demonstrated cationic antagonisms. HOAGLAND (12), LUNDEGXRDH (18), and RICHARDS (22) summarized the interactions existing in the absorption of potassium, calcium, magnesium, and sodium. Possible ways in which one element in nutrition may substitute for another are outlined by COOPER (6). A decrease in plant growth and an accentuation of mineral element deficiency symptoms by unbalanced soil cations have also been demonstrated by many investigators (7, 8, 17, 21, 28). The concept that a lack of balance may be more harmful to plant growth than a deficiency of two or more nutrients has been suggested. The reports of DAVIDSON and BLAKE (9), and of WAUGH, CUTLLINAN, and SCOTT (31), and recently those of BROWN (4) on nutrient balance in the peach bear this out. PHILLIPS, SMITH, and HEPLER (20) reached a similar conclusion with the tomato plant. During the past six years at the Missouri Agricultural Experiment Station, the importance of nutrient balance in obtaining maximum response to fertilizer treatment has been repeatedly observed in nutritional studies with vegetables. This report deals with the yields of some vegetable crops as in'Missouri College of Agrieultural Journal Series no. 1010. 244