engleski

AGRONOMIC AND DIETARY VALUE OF PAK CHOY (BRASSICA RAPA SSP. CHINENSIS) IN DIFFERENT GROWING PERIODS

Pak choy, in Croatia a less known oriental leafy vegetable species, can be found on the Croatian market in the winter period as an import from other Mediterranean countries. The purpose of the investigation was to obtain information about its agronomic traits and dietary value in different growing periods (two spring and a summer-autumn in the open, and an overwinter period in an unheated high tunnel) from 1998 to 2000. Open field trials were laid out according to the split-plot scheme in five replications, with plant density as the main factor (16.7 and 22.2 plants/m2) and harvest dynamics as the sub-factor [(30, 37 and 44 days after planting (DAP)]. The mono factorial overwinter trial was set up so as to involve supplementary direct covering with polypropylene material (PP) and no covering, at a plant density of 16.7 plants/m2. Undesirable bolting was recorded in spring growing periods (0%, 0 to 9% and 5 to 40% at harvest 30, 37 and 44 DAP, respectively) and in the winter period (with PP covering 2 to 10%, without covering 6 to 20%). Contents of leaf petioles and blades in the rosette mass were about equal in the harvest 30 DAP in both spring periods (ca 45%), and it increased as the vegetation progressed to the advantage of petioles (to 64% at 44 DAP in the summer-autumn period, to 60 % in the overwinter crop). The highest contents of total dietary fibres (0.56 to 0.79 g/100 g fresh matter) and biogenic elements (N, P, K, Ca, Mg, Fe, Mn, Zn and Cu), as well as significantly lower contents of nitrates (1104 to 1187 mg/kg fresh matter) were recorded in the spring growing periods. Closer spacing and supplementary direct crop PP covering had a positive effect on yields (P≤ 0.01) and mainly no significant effect on the other traits studied.

growing periods; plant density; harvest dynamics; bolting; yield; dietary fibres; nitrates; biogenic elements

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