Evaluation of Bibb (Butterhead) Lettuce for Hydroponic Production in Saskatchewan Greenhouses Full Report (2016) - 28 pages
Lettuce has excellent potential as a greenhouse crop in Saskatchewan. Lettuce is in demand year round and it grows well under low light levels and cool temperatures – making lettuce well suited for production during winter months. Profitable greenhouse production depends on growers using production practices which maximize productivity and quality while minimizing costs. Selection of well-adapted cultivars is a cost effective means of enhancing productivity and quality. This project sought to evaluate cultivars of lettuce suited to hydroponic production. Performance factors evaluated included speed of development, tolerance of biotic (disease and insects) and abiotic stresses (heat, cold, low light and nutrient imbalances), as well as head size, appearance, texture and flavor. A total of 53 cultivars of Bibb type (aka. Butterhead, Buttercrunch) lettuce were demonstrated over 25 production cycles which ran from January 2012 through June 2014. The lettuce plants were grown for 4 weeks in rockwool or Jiffy pots prior to being moved into the NFT-type hydroponic production system. Through progressive production cycles growing methods were modified in an effort to enhance productivity and quality. After testing many fertility regimes – excellent crop growth and quality could be achieved using a simple fertilizer program based on using a readily available complete fertilizer product (7-11-27+micros) supplemented with calcium nitrate and ammonium sulfate. The lettuce crops reached marketable size within 3-4 weeks of transplanting into the hydroponic system. The rate of crop growth varied with the amount of light available to the crop. Supplementing natural light with artificial light (125 umol/m2 for 16 h/day from a HPS system) enhanced crop growth and quality during the winter months. Cultivars that produced looser heads tended to be higher yielding and had fewer problems with tipburn than the semi-head types. Of the loose head types - Red Sails (Johnny’s Seed), Two Star (Stokes) and Simpsons Elite (Stokes) consistently produced large attractive heads with good flavor and minimal tipburn. Optima (Osborne Seeds), Adriana (Johnny’s), Natalia (Paramount) and Santoro (Rijk Zwaan) were the best semi-head types – combining good yields and appearance with only moderate grade out to tipburn.