Effect of Calcium Cyanamide as an Alternative Nitrogen Source on Growth, Yield, and Nitrogen Use Efficiency of Short-Day Onion

Abstract

Effective nitrogen (N) management in agriculture is vital to optimize crop growth and yield while minimizing environmental impact. Conventional nitrogen (N) sources, such as urea, have limitations in promoting growth and reducing N leaching. A two-year field experiment was carried out to investigate the effects of calcium cyanamide (CaCN2) as a slow-release N source on short-day onion growth, yield, and N use efficiency (NUE). Six types of N sources were administered: (i) an initial application of 80 kg ha−1 N in the form of CaCN2 before planting; (ii) an initial application of 80 kg ha−1 N in the form of CaCN2 before planting, followed by a topdressing of 50 kg ha−1 N in the form of limestone ammonium nitrate (LAN); (iii) an initial application of 80 kg ha−1 N in the form of CaCN2 before planting, followed by a topdressing of 50 kg ha−1 N in the form of urea; (iv) an initial application of 80 kg ha−1 N in the form of LAN before planting, followed by a topdressing of 50 kg ha−1 N in the form of LAN; (v) an initial application of 80 kg ha−1 N in the form of urea before planting, followed by a topdressing of 50 kg ha−1 N in the form of urea; and (vi) control (0 kg ha−1 N). Preplant CaCN2 (80 kg ha−1 N) outperformed the standard fertilizers used in onion as an N source (urea and LAN) by improving growth and yield, and reducing N leaching. Preplant CaCN2 topdressed with either LAN or urea led to a significant increase in plant growth and total yield compared to using LAN or urea alone. The application of CaCN2, followed by topdressing with either LAN or urea, decreased onion bolting by 1.6% and 1.83%, respectively, compared to the control. The study suggests that applying LAN or urea as a topdressing to preplant CaCN2 enhances N utilization efficiency, leading to increased onion bulb yield and quality while reducing N leaching. This approach can help mitigate farm-level environmental pollution and provide valuable insights for improving onion production and sustainable agriculture practices in South Africa.

Optimizing Nitrogen Nutrient Management for the Sustainable Enhancement of Secondary Metabolites and Yield in Onion Cultivation

“…Simultaneously, within the N+Sfertilized variant, the white variety Pueblo exhibited a 10% elevation in flavonoid levels compared to the control variant (without fertilization). The study from 2024 highlighted the significant potential of optimizing nitrogen fertilizer sources to enhance the nutritional quality of white short-day onions, encompassing phenolics, flavonoids, and free radical scavenging activity-specifically, the synergistic effect of pre-plant CaCN2 application (80 kg N ha −1 ) [39]. However, it is conceivable to suggest that the experimental combination of N+S fertilizers may increase the level of flavonoids in onion varieties, with a more pronounced enhancement observed in red onion varieties.…”

Effects of Nitrogen Source on Mineral Element, Phytochemical Content, and Antioxidant Activity of Short-Day Onion (Allium cepa) Bulbs

“…For each treatment, six bulbs of uniform size were meticulously chosen for mineral analysis. Subsequently, freeze-dried onion samples ground into fine powder underwent The application of fertilizer was conducted as described by Simelane et al [21]. Preplant fertilization was determined by soil analysis and included 2000 kg ha −1 calcitic lime (except for CaCN 2 treatments), 300 kg ha −1 superphosphate (10.5% P), 150 kg ha −1 potassium sulfate (22.4% K and 18.4% S), and 150 kg ha −1 magnesium sulfate (10% Mg and 13% S), which were broadcasted.…”

“…This increase could be attributed to a combination of factors. These factors include the role of calcium from CaCN 2 in maintaining cell wall integrity [52,53], reduced leaching due to CaCN 2 [21,40], and balanced nutrient uptake [50]. This balance results from the immediate availability of N from urea and LAN, as well as the continuous supply of N from the slow-release CaCN 2 .…”

“…These losses contribute significantly to the escalating problem of environmental contamination [20]. To combat this issue, environmentally conscious methods are being explored, such as integrating slow-release fertilizers into cultivation practices [20][21][22].…”

“…Within the realm of slow-release fertilizers, Perlka ® (AlzChem, Trostberg, Germany), also recognized as calcium cyanamide, emerges as a promising contender, especially suited for crops in regions characterized by high rainfall [21,38]. This fertilizer not only stimulates beneficial soil organisms, thereby enhancing soil fertility, but also provides calcium in a readily accessible form, ensuring robust cell walls and healthier plants [21,[38][39][40]. Despite its significant positive impact on various crops, there exists a dearth of research investigating its effects on the mineral composition and secondary metabolite production in onions.…”