|Authors: ||Z. Premuzic, F. Vilella, A. Gárate, I. Bonilla|
|Keywords: ||Lactuca sativa, light, nitrogen fertilization, compost, nitrates, vitamin C|
Lettuce cv. `Mantecosa’ was field and greenhouse grown during autumn-winter to study the incidence of N fertilization (organic and mineral) and light supply on production and quality (nitrates and vitamin C). Three N fertilization (100 kg/ha total N), two organic (vermicompost and biostabilized compost) and one mineral (74% Ca (NO3)2 + 6 %NH4N03 + 20% urea) and a control (without fertilization) treatment were applied.
Greenhouse lettuce received different light conditions for each treatment: 24 hour light supply (120 W.m-2) and no artificial light supply.
Fresh weight, vitamin C, and nitrates were determined at commercial maturity.
Field production had 37-60% larger yields, 32-35% less nitrates and 39-52% higher levels of vitamin C than greenhouse production.
Light supplied for 24 hr resulted in larger yields and lower content of nitrates for all fertilization treatments in greenhouse.
Urea and vermicompost plots resulted in the largest yield in the field, while vermicompost and biostabilized compost had the largest yield in the greenhouse.
The lowest nitrates and largest vitamin C concentration occurred in production systems with biostabilized compost or the control.
A positive correlation occurred between plant weight and nitrate and negative correlation between plant weight and vitamin C for field-grown lettuce.
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