Abstract
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.
Highlights
Endive (Cichorium endivia L. var. crispum) is a leafy green vegetable belonging to the Asteraceae family, native to the eastern Mediterranean region and probably originated from the cross between C. intybus and C. pumilum [1,2]
In spring-summer season, nitrogen-unfertilized plants had the lowest head fresh weight (Table 2). The latter was not significantly affected by the type of supplied nitrogen, as it ranged from 363.87 g in plants grown with 100 kg N ha−1 as ammonium nitrate (100AN) to 375.40 g in plants supplied with 50 kg N ha−1 as ammonium nitrate (50AN) -50CC
Data collected on head height, stem diameter and visual quality, number of leaves and head dry matter supported the trend established for the head fresh weight (Table 2)
Summary
Endive (Cichorium endivia L. var. crispum) is a leafy green vegetable belonging to the Asteraceae family, native to the eastern Mediterranean region and probably originated from the cross between C. intybus and C. pumilum [1,2]. Nitrogen above-optimal fertilization of vegetable crops represents a potential risk for human health. We assume that curly endive, less cultivated than other leafy vegetables, is prone to NO3 − accumulation in the leaves when subjected to above-optimal nitrogen fertilization. CaCN2 is a well-recognized nitrogen fertilizer, in the vegetable crop sector, and it may represent a valuable alternative to traditional soluble fertilizers. It may improve the crop NUE [12] through a better modulation of N supply [13]. Several researches have demonstrated that nitrogen use efficiency (NUE) and NO3 − accumulation are affected by numerous interrelated factors such as fertilization rate and source, irrigation type, and growing season [14,15,16,17,18,19,20]
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