No abstract

Protecting the environment by improving the crop-system nitrogen (N) use efficiency (NUE) while maximising yield and quality is a primary challenge for modern agriculture, and understanding the processes that govern N fluxes in the plant-soil system is essential to improve NUE. An on-farm study was conducted over two fall-winter seasons to evaluate the NUE, agronomical and physiological response of romaine (var. longifolia, cv Manavert) and red oak-leaf (var. crispa, cv Aruba) lettuce (Lactuca sativa L.) to different N-rates (0, 60, 120, 180 kg ha -1 of N). Nitrogen rate influenced all tested parameters, including plant fresh and dry weight, N accumulation, leaf NO3 -and dry matter content, NUE indices, N nutrition index (NNI), soil residual N and the estimated N losses at the end of the crop season. Fresh yield, dry weight and N-accumulation response to N rate were influenced by lettuce genotype. Manavert had higher N recovery, NUE, and lower leaf NO3 -concentration than Aruba. Analysing the NNI overtime, 120 kg ha -1 of N assured an optimal N status in both Manavert and Aruba, while N deficiency and excess were observed at lower and higher N-rates, respectively. An empirical relationship was observed between NNI and leaf NO3 -concentration, suggesting that leaf NO3 -concentration may be used to predict NNI and thus the crop N status. The relationship between NNI and leaf NO3 -concentration may be used to define optimal leaf NO3 -concentration ranges for the rapid and site-specific assessment of the crop N status, and the dynamic adjustment of N-fertilisation, contributing to improve crop NUE, minimise N-losses, and optimise yield and quality of lettuce crops.

Core Ideas Calcium cyanamide may be a good N fertilizer source for lettuce crops. Calcium cyanamide can reduce nitrate accumulation in lettuce crops. Calcium cyanamide did not improve lettuce crop N use efficiency. Lettuce genotypes influence the crop N uptake and N utilization efficiency. A 2‐yr field study was conducted to evaluate the effects of calcium cyanamide as an alternative nitrogen (N) fertilizer source on N use efficiency (NUE), yield, and quality of two types of lettuce (Lactuca sativa L.), romaine (var. longifolia, cv. Manavert) and red oak‐leaf (var. crispa, cv. Aruba), grown on clay soil under a Mediterranean environment. Pretransplanting application of 120 kg ha−1 of N as calcium cyanamide (120CC) was compared with a traditional split application of 120 kg ha−1 of soluble N (120SN) consisting of 50% ammonium sulfate applied before transplanting and 50% as ammonium nitrate applied after transplanting. An unfertilized control (0‐N) was included to calculate NUE indices. At harvest leaf area index, dry weight, fresh yield, dry matter concentration, and NUE indices were not affected by the N source. Leaf nitrate (NO3−) content was on average 55 and 41% higher in Aruba than in Manavert in the first (Exp‐1) and second (Exp‐2) season, respectively. Plants fertilized with 120CC had lower leaf NO3− content (41 and 18% in Aruba and 70 and 21% in Manavert in Exp‐1 and Exp‐2, respectively) compared with those fertilized with 120SN. These results suggest calcium cyanamide may be used as an effective tool to reduce leaf NO3− accumulation and to produce high‐quality lettuce in compliance with European Regulation No. 1258/2011 while assuring competitive yields.

No abstract