Nitrogen source and application timing affect growth and reproductive performance of gherkin (Cucumis sativus L.)

Abstract

Gherkin (Cucumis sativus L.) is a high-value, export-oriented crop in Sri Lanka, where optimal fertiliser management, particularly application time, plays a critical role in enhancing vegetative and reproductive performance. This study evaluated the effects of two nitrogen sources (urea and calcium nitrate - CN) applied as first top-dressing 10, 15, 20, and 25 days after seedling emergence, followed by repeated applications every 10 days up to 60 days. The experiment used a factorial randomised complete block design (RCBD) with six replicates. Growth parameters assessed plant height at 50% flowering and first harvesting stages, the number of side shoots/plant at 70 days, and the leaf area of the 14th leaf at full maturity. Reproductive parameters included the number of flowers/plant and days to flowering from seedling emergence. Data were analysed using two-way ANOVA, and means were compared using Duncan’s Multiple Range Test at P < 0.05. Applications at 10 and 15 days resulted in significantly higher plant height at the 50% flowering stage (111.6 cm and 107.1 cm), at the first harvesting stage (150.2 cm and 147.7 cm), and the highest number of side shoots/plant (19.8 and 18.5). Significant interaction was observed only for the leaf area of the 14th leaf, with the highest values under urea at 10, 15, and 20 days (278.3 cm2, 271.7 cm2, and 260.2 cm2), and CN at the same timings (218.4 cm2, 260.9 cm2, and 232.4 cm2). Days to flowering from seedling emergence were significantly influenced by application timing, with the earliest flowering at 10, 15, and 20 days (22.5, 22.5, and 23.2 days). The number of flowers/plant was significantly affected by both nitrogen source and application timing, with urea producing the most flowers (43.8) and the highest counts observed at 10 (49.0) and 15 (41.2) days. Overall, these results suggest that top-dressing at 10 and 15 days after seedling emergence optimised gherkin growth and reproduction, with timing being the critical factor and urea particularly enhancing reproduction, although these findings remain preliminary until yield is evaluated.