Effect of agronomic management practices on lettuce quality

Summary

The effect of different agronomic strategies on the nutritional quality of head lettuce was investigated. The factors included were irrigation type, fertiliser input type and level. The assessed ingredient parameters were nitrate, lutein, ß-carotene and polyphenols. Hygiene was described by total aerobic bacterial count and number of coliform bacteria, Escherichia coli, Salmonella enteritidis, Enterococcus and Enterobacteriaceae. Lettuce treated with mineral nitrogen fertiliser (calcium ammonium nitrate) displayed a higher nitrate content than lettuce treated with organic manures (fresh farmyard manure (FYM), rotten FYM (fermented nettle extract). Nitrate concentration in lettuce tended to increase with increasing amounts of fertiliser, independent of fertiliser type. Fertiliser type and level also affected the carotenoid content. Rapidly available nitrogen from mineral fertiliser gave higher lutein levels compared with slowly released nitrogen. Similar results were observed for ß-carotene. There were no obvious differences regarding polyphenols for the different modes of fertiliser input. The bacteriological quality was only marginally or not at all influenced by the type of fertiliser.