Plant growth and calcium and potassium accumulation in lettuce under different nitrogen regimes of ammonium and nitrate nutrition

Effects of varying the ammonium:nitrate ratios in nutrient solutions and effects of calcium carbonate buffering on plant mass and accumulation of potassium and calcium were studied with two lettuce (Lactuca sativaL.) cultivars, Two Star and Red Deer Tongue, in a greenhouse hydroponics experiment. The supply of ammonium-N ranged from 0% to 100% of the total nitrogen in the nutrient solution at 0.015 M total N supplied as nitrate and ammonium. Proportions of ammonium-N greater than 50% of total N nutrition severely curtailed growth and calcium and potassium accumulation for both cultivars. Growth and composition of the two cultivars did not differ in response to nitrogen nutrition. The acidity of the nutrient solution increased as the proportion of ammonium increased. Application of calcium carbonate buffering improved growth in solutions containing ammonium, but plants did not attain the amount of growth and nutrient accumulation achieved with solely nitrate nutrition.

Automated summary

The study found that providing more than 50% of the total nitrogen as ammonium-N in hydroponic nutrient solutions significantly inhibited growth and accumulation of calcium and potassium in lettuce. The acidity of the nutrient solution increased as the proportion of ammonium-N increased. While applying calcium carbonate buffering improved growth in solutions containing ammonium, it did not reach the growth and nutrient accumulation levels achieved with solely nitrate nutrition.