Studies on the growth rate and nutrient absorption of head lettuce

Abstract

does not appear. First page follows. Introduction California ranks first among the states in the commercial production of lettuce (Lactuca sativa L.), averaging slightly over 60 per cent of the national monetary value (Dean and McCorkle, 1960); (Hoos and Phelps, 1948).4 Spring, summer, and fall production is concentrated in the central coastal region of the state, and the winter crop is grown in the warmer interior desert areas of the Imperial and Palo Verde valleys. For such an important crop, only limited information is available regarding the rate of growth and course of nutrient absorption (Fujimura et al., 1960); (Lorenz and Minges, 1942); (McGeorge et al., 1940); (Veihmeyer and Holland, 1949). A thorough knowledge of the growth pattern and nutrient uptake of lettuce is essential to a better understanding of its fertility requirements, as well as insect and disease control in the crop. The purpose of this study was to determine the growth rate and nutrient absorption of the Great Lakes variety of lettuce during development for the spring, summer, and fall crops in the Salinas Valley of California. Although this study was restricted to the Salinas Valley, the information reported is also applicable to the Great Lakes variety when grown in other central coastal districts of California, because of the similarity in growing conditions. Methods and Materials Culture and Growth Measurements During 1957 and 1958, seventeen commercial fields in the Salinas Valley were selected for study. The trials were located on seven soil types that were representative of the lettuce-production area. Thermograph records were kept of the air temperatures six inches above the ground during the growing period of each of the crops.