The objective of the experiments was to determine the values of the agronomical melon (Cucumis melo L.) leaf indices, represented by both area (FLA) and dry weight (FLW) of the fifth leaf from the apex associated with the nitrogen rate for the maximum melon fruit yield (MFY), at two samples dates and two environmental conditions. Two experiments, in unheated greenhouse and field conditions, were carried out with similar procedures. Each experiment consisted of four randomized blocks containing five treatments or five nitrogen rates (0, 75, 150, 300, and 450 kg ha-1 of N), applied as urea. Part of the fertilizer was placed in furrows (30%), before seedling transplantation, and the remaining 70% were trickle-applied through part of the plant cycle. Initially, 14 days after transplantation, plant chlorosis intensity was evaluated by scores from 0 (no chlorosis) to 5 (leaves completely chlorotics). At 25 and 53 days after transplantation, at first and second fruit setting, FLA and FLW were determined. At both experiments, chlorosis intensity decreased, FLA and FLW increased with increasing N rates. Chlorosis intensity values associated with MFY were 0.22 and 1.11 at greenhouse and field, respectively. In the greenhouse, at first and second sampling dates, FLA values associated with MFY were 107 and 72 cm² and FLW values were 0.36 and 0.26 g, respectively. In the field, the corresponding values were 89 and 69 cm² and 0.39 and 0.30 g, respectively. These are proposed melon plant index values indicators of the added N fertilizer rate adequacy.
Cucumis melo; cantaloupe; diagnostic; leaf area; leaf dry weight
