Growth, Critical N Concentration and Crop N Demand in Butterhead and Crisphead Lettuce Grown under Mediterranean Conditions

• Main Authors: Giulia Conversa, Antonio Elia
• Format: Article
• Language: English
• Published: MDPI AG 2019-10-01
• Series: Agronomy
• Subjects: growth; specific leaf nitrogen; nitrogen use efficiency; critical nitrogen uptake
• Online Access: https://www.mdpi.com/2073-4395/9/11/681

Excessive nitrogen (N) fertilizers are applied in lettuce causing both environmental issues and N crop luxury consumption. In order to improve the N use efficiency (NUE) by defining optimal crop growth and N requirements of butterhead and crisphead lettuce, two field experiments were conducted using 0, 50, and 100 kg ha^−1 of N fertilizer to study (i) the growth and productivity, (ii) the NUE, (iii) the critical N dilution curve, and (iv) the N demand. Nitrogen supply enhanced dry weight (DW) accumulation in the butterhead (from 295 to 410 g m^−2), but not in the crisphead type (251 g m^−2). The NUE indices underlined the poor ability of the crisphead type in absorbing soil N and also in the utilization of the absorbed N for producing DW. The critical N dilution curves %Nc = 3.96 DW^−0.205 and %Nc = 3.65 DW^−0.115 were determined for crisphead and butterhead lettuce, respectively. Based on these type-specific %Nc curves, the estimated N demand was 125 kg ha^−1 in the butterhead and 80 kg ha^−1 in the crisphead lettuce for producing 4.3 and 2.5 Mg ha^−1 of DW, respectively, under Mediterranean climate. Neither N fertilization nor genotype affected crop productivity.