LIGHT CONDITIONS, TIMING FERTILIZATION AND WATER AVAILABILITY INFLUENCE ON NURSERY DEVELOPMENT OF LETTUCE SEEDLINGS AND THEIR EFFECT ON FIELD PRODUCTIVITY.

The seeds were planted in a medium peat substrate on 5 July 1988. The growth conditions compared in factorial combinations were:

1. growing medium humidity: container capacity (CC) and 0.7 CC;
2. light conditions: natural light and reduction of the light intensity by 50%;
3. fertilization: fertilization only in the initial nursery growth phase and during the entire period (21 days) with the same quantity of solution at 2%.

The plants were checked twice in the nursery and the following results were noted: length of the longest leaf (cm), number of leaves, fresh weight (mg), dry weight (mg), dry weight/fresh weight, leaf area (cm²); in the field the weight and diameter of the head were measured.

The results show that during in-nursery growth, reducing light decrease the % of dry matter, the fresh weight and the dry weight of plants as well as the number of leaves; fertilization in the initial growing phase, only results in a greater accumulation of dry weight (%). The field production is not influenced by the substrate humidity during in-nursery growth, whereas more light increases the weight and diameter of the head; fertilization in the 1st period (in the nursery) does not affect the weight, but reduces the diameter of the head.

The analysis of the regression between the final production and the in-nursery growth parameters showed that there is a positive relationship between the accumulation of dry weight in plants in the initial in-nursery growth period and the weight of the heads produced in the field.

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