Predicted effect of temperature and n fertilization on crop response of four cultivars of head lettuce

Abstract

An investigation was conducted on an Olivier silt loam (fine‐silty, mixed, thermic aquic, Fragiudalfs) at two locations to determine the influence of 6 seasonal temperatures and 4 N rates on head diameter, head weight, tissue NO₃ concentration and crop yield of 4 head lettuce (Lactuca sativa L.) cultivars. An analysis of covariance was used to establish prediction equations for each dependent variable. Temperature was shown to have a significant curvilinear influence on all crop parameters. There was a significant cultivar X temperature interaction with respect to all dependent variables except tissue NO₃ concentration. Calculated optimum mean temperatures for maximum head diameters, head weights, and yields for all cultivars were found to range between 17.4° and 18.2°C.

Fertilizer N effects were significant on head weight and crop yield. Nitrogen rate did not significantly affect young leaf tissue N0₃ concentration. Greater tissue NO₃ levels were found at lower temperatures in the covariate range.

At optimum temperatures, the cultivar ‘Fairton’ produced larger diameter heads and greater yields.