Yield and Quality of Crisphead Lettuce Cultivated on Organic or Mineral Soils

Abstract

ABSTRACT A 2-year experiment was conducted to determine the potential for crisphead lettuce production on mineral soils compared to the production on organic soils of Quebec, during the warmest period of the season when quality often decreases. For each soil type, there were three experimental sites and two planting dates. For each soil type by site by planting date combination, three varieties, ‘Ithaca’, ‘Emperor’ and ‘Salinas 88’ were tested within four blocks. Transplanting occurred from 11 to 28 June 1999, and from 11 June to 5 July 2000, and harvest was from 21 July to 5 August 1999, and from 27 July to 10 August 2000. Lettuce on organic soils matured 4 to 7 days earlier and generally produced larger and heavier, firmer and more uniform heads. Soil type did not affect percentage of heads with the physiological disorders rib blight and tipburn. ‘Ithaca’ produced large, heavy and very firm heads, particularly on organic soil. Although this variety showed tolerance to bolting, it was susceptible to rib blight (50%), but less to tipburn (19%). ‘Emperor’ had heads that were lighter than those of the other two varieties on organic soil and matured later, and it had significantly less rib blight (22%) but more tipburn (34%) than the other two varieties. Although it produced a head with good weight, ‘Salinas 88’ tended to be fluffy and bolted early on both soil types. The potential for mid-season production of crisphead lettuce seems limited under current production methods.