Artificial irradiation for lettuce plant raising - technical and economic aspects.

Abstract

In November and December lettuce seeds were sown direct in soil blocks and the seedlings raised under natural light alone or supplemented with 200 W/m2 for 16 h daily. A night temperature of 7 deg C and a day temperature of 12, 15, 18 or 21 deg plus a 3 deg light-dependent increase were maintained. The seedlings were planted out in mid-January and harvested in mid-March. Plant growth was far more rapid, resulting in early maturity, where supplementary lights had been used initially and in addition the foliage was sturdier and broader. However, a comparison of the costs of production for lighted and unlighted plants of the same weight at planting showed that the extra cost of lighting was not justified by a marked increase in yield under the conditions of the trial. (Abstract retrieved from CAB Abstracts by CABI’s permission)