Head lettuce growth and nutrient absorption studies indicate need for re-evaluation of fertilizer practices

In Salinas Valley trials, Great Lakes lettuce produced more than 70% of its fresh weight during the 21 days before first harvest—and absorbed over 70% of the total nutrient uptake of the crop during the same period. These results indicate that the practice of some growers using a preplant application of from one-half to two-thirds of the total amount of nitrogen to produce the crop is questionable. Since lettuce absorbs little nitrogen in the early phase of growth, a more realistic program would include preplant applications of only one-fourth the amount of total nitrogen to be used and two side-dressings to apply the balance—one after thinning and a second a month before the predicted first harvest.