Nitrogen efficiency and yield responses of two ‘early’ globe artichoke cultivars to nitrogen fertilization

Nitrogen (N) fertilization is extremely important in determining horticultural crop growth and yield performance. However, the demand for environmentally sustainable production systems leads modern agriculture to optimize the efficiency of N fertilizer applications. Among the high N-demanding horticultural crops, globe artichoke deserves particular attention since farmers often apply N rates up to 700 kg ha‑1 with possible environmental impact. In order to minimize N supply while maintaining optimal agronomic performances, this study investigated the effects of three N fertilizer rates (0-200 and 400 kg ha‑1, referred to as N0-N200 and N400, respectively) on crop performances of two early globe artichoke cultivars ( Violet de Provence and Tema 2000 ). The field trial was conducted during 2013-14 on the Catania Plain (Sicily), a typical area for globe artichoke cultivation in Italy. Heads were weekly harvested at the marketable stage, weighted to determine their fresh weight and then oven-dried to determine their dry matter content. The following parameters were also calculated: earliness, total yield, harvest index (HI) and N agronomic efficiency (NAE). In addition, chlorophyll content was recorded at 82-132 and 181 days after planting (DAP). The results indicated that N supply strongly affected all the above-mentioned traits. Compared to control (N0), earliness and harvest index increased up to N200, while they significantly decreased with N400. Both cultivars reported a significant reduction of NAE due to the increase in N supply from 200 (2.3 ∆ kg ha‑1 DW kg‑1) to 400 kg ha‑1 (0.6 ∆ kg ha‑1 DW kg‑1). Only N200 increased the fresh weight of main, first and second order heads than N0. In addition, regardless of measurement time, N200 also ensured an optimal chlorophyll content (as SPAD units). Finally, it emerged that it could be possible to decrease nitrogen supply from 400 to 200 kg ha‑1, while increasing at the same time agronomic performances of the crop and ensuring a more environmentally sustainable production.