Studies on the growth rate and nutrient absorption of onion

Abstract

This paper reports the development and nutrient absorption of plants of the onion cultivar Southport White Globe, growing in the field. Growth curves for leaf number, plant height, plant fresh and dry weight, and per cent dry matter are presented. The onion plants produced more than 64 per cent of their fresh weight and more than 72 per cent of their dry weight during the period of bulbing to harvest. Approximately 28 per cent of the fresh weight and 36 per cent of the dry weight of the plants were produced after tips of the leaves dried and tops had begun to collapse. Chemical analyses of the plants showed that total N, P, K, Ca, Mg, and Na tended to decrease during plant growth. At harvest, total N and P were higher in the bulb than in the whole plant; K, Ca, Mg, and Na were lower. Nutrient uptake curves of two crops are presented. Maximum rate of growth during bulbing was accompanied by maximum rate of nutrient uptake. At harvest the crops had removed, in pounds per acre, averages of: N, 143; P, 23; K, 113; Ca, 87; Mg, 13; and Na, 10.