Production and commercial quality of lettuce fertirrigated with nitrogen and potassium in greenhouse

ABSTRACT

Organic fertilization can provide most of the nutrients needed to grow lettuce crop. However, the rate of nutrient mineralization may be limiting to absorption, once complementary forms of fertilization with soluble fertilizers can be used, such as fertirrigation. The objective of this work was to evaluate the effect of the drip fertirrigation with nitrogen and potassium with organic fertilization in the production and commercial quality of the Vera lettuce cultivated in greenhouse. The cultivation period used for the experiment was between August and October 2012 (winter and spring; 67 days). The experimental design was completely randomized with three replications, in which ten treatments were evaluated, with nine of them formed by the Plan Puebla III matrix, that is, from the combination among five N (9, 54, 90, 126, and 171 kg ha^-1) and five K doses (1.15, 6.90, 11.50, 16.10, and 21.85 kg ha^-1), applied in topdressing, and one of them as control, which did not receive fertirrigation. The best answer to the shoot commercial fresh mass took place with the maximum dose of Si and K₂O and in the zero dose of N. The commercial leaf number per plant showed their higher values in the maximum doses of N and Si and K₂O. The shoot noncommercial fresh mass increment, both with the increase in N doses and with the increase in Si and K₂O doses, did not harm the commercial quality.

Key words:
Lactuca sativa L.; micro-irrigation; greenhouse; commercial fresh mass.