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

Abstract

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 sativa L.) 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.

Keywords:

• Ammonium toxicity
• hydroponics
• Lactuca sativa
• solution acidity

Acknowledgement

This research was supported by the Masschusetts Agriculural Experiment Station Project 538 and The Stockbridge School of Agriculture of the University of Massachusetts, Amherst.