An appraisal of calcium cyanamide as alternative n source for spring-summer and fall season curly endive crops: Effects on crop performance, NUE and functional quality components

A two-year study was conducted in both spring-summer and fall seasons to evaluate calcium cyanamide (CaCN2) as an alternative nitrogen (N) source for curly endive (Cichorium endivia L. var. crispum) grown in a Mediterranean environment. Four types of N applications were administered: (i) pre-transplanting base application of 100 kg N ha−1 corresponding to 100% of the supplied N (100CC), (ii) pre-transplanting base application of 50 kg N ha−1 corresponding to 50% of the supplied N (50CC) complemented with 50 kg N ha−1 as ammonium nitrate (50AN) supplied through fertigation, (iii) standard application of 100 kg N ha−1 as ammonium nitrate (100AN) supplied entirely through fertigation, and (iv) a N-deprived control (0 kg N ha−1) used as base reference to calculate the N use efficiency indices (NUE). Fall season increased head fresh weight, head height, stem diameter and plant visual quality, compared with the spring-summer season. The CaCN2 and standard fertigation N applications were equally effective in increasing head fresh weight and other physical parameters such as, head height, stem diameter, visual quality, number of leaves and head dry matter when compared to the unfertilized control. However, in spring-summer season, CaCN2, especially when applied straight at 100 kg N ha−1, effectively increased ascorbic acid and total phenolic content, whereas, in fall season, an increase in TSS and ascorbic acid was recorded. In both, spring-summer and fall seasons, CaCN2 significantly decreased N content and nitrogen accumulation (Nacc). Furthermore, CaCN2 pre-transplant application improved NUE indices both in terms of N fertilizer recovery efficiency and in terms of physiological efficiency of applied N. Our results finally demonstrated that NUE indices increased in the fall season as compared to the spring-summer season.