Biomass and nutrient concentration of lettuce grown with organic fertilizers

Abstract

The responses of lettuce (Lactuca sativa L. ‘Arroyo’) to organic nitrogen (N) fertilizers were investigated in a greenhouse. Fertilizers were blood meal (BLO), feather meal (FM), cottonseed meal, alfalfa meal, sewage sludge, compost, cow manure, a chemical fertilizer, and a treatment without fertilizer. Amounts of N from fertilizers were 100, 200, 400, or 800 mg per pot. Lettuce yield was higher for plants receiving fertilizers than with no fertilizer and increased with increased N applications, but high applications of BLO or FM suppressed yields. Nitrogen and nitrate increased in leaves as N supply increased with all fertilizers. Small changes in leaf nutrient contents other than N occurred among or with increased application of the various fertilizers. The soil carbon dioxide release and ammonia volatilization were high from fertilizers with high N concentrations. Organic fertilizers with high N increased lettuce growth at lower applications than those with low N content.

KEYWORDS:

• ammonia volatilization; nutrient concentration in vegetables; respiration; seed germination

Acknowledgments

This research was conducted with the support of The Stockbridge School of Agriculture and the Massachusetts Agricultural Experiment Station Project MAS 459. The authors thank Dr. Wesley Autio for his guidance, suggestions, and comments for statistical analysis. They also appreciate Dr. Sarah Weis for support in the laboratory measurements of nutrients.