Azure Adams

Carrot Yield and Quality as Influenced by Nitrogen Application in Cut-and-Peel Carrots

Root bulking, quality, and uniformity in cut-and-peel carrots (Daucus carota) are paramount for optimizing marketable yield and quality. Root bulking is an ecophysiological manifestation in response to inputs such as fertilizers. Understanding this ecophysioloical interaction will help to optimize yield, quality, and amount of inputs used. Three years of field trials were conducted in Kings County, Nova Scotia, to investigate the effects of varying levels of nitrogen (N) fertilizer on yield, recovery, and root and tissue N of two cut-and-peel varieties, Sugarsnax and TopCut. Seven levels of ammonium nitrate (34–0–0; 0, 50, 100, 150, 200, 300, and 400 kg N h−1) were hand broadcast in a split (60% pre-emergence and 40% 8 weeks after emergence) application. No significant interactive effects of N and variety in terms of gross yield or recovery were observed, though Sugarsnax total yields were 12.7% greater than those of TopCut. Overall, optimum yields were achieved at N rates of 150 kg N h−1 and further addition did not significantly improve yield or quality. Increased N significantly increased root and tissue N, but N concentration in both tissues peaked at the 300 kg N h−1 rate. However, neither root nor leaf tissue N had any effect on marketable or total yield. These results show that root bulking is not modulated by altering N applications, and the results also suggest that carrots may have high N-use efficiency or harness N from deeper zones.

Ecophysiological characteristics of two carrot (Daucus carota L.) cultivars in response to agroecological factors and nitrogen application

Plant density, planting time, harvest timing, and nitrogen influence on short-term gas-exchange properties of carrot cultivars, Topcut and Sugarsnax (Daucus carota L.) were investigated under field conditions. Net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) differed significantly with the cultivars studied. Both planting and harvest timing changed the midday PN rates. PN increased as harvest timing advanced regardless of planting time. Late planting combined with late harvesting registered the maximum PN rates (4.5 μmol m−2 s−1). The water-use efficiency (WUE) was altered by temperature at different harvest timings along with the choice of cultivar. Early harvested Sugarsnax had a higher WUE (2.29 mmol mol−1) than TopCut (1.64 mmol mol−1) as Sugarsnax exhibited more stomatal conductance than TopCut. These changes were principally governed by fluctuations observed with air temperature and photosynthetic photon flux density (PPFD) and altered by the sensitivity of the cultivars to ecological factors. Plant density did not affect the photosynthetic gas-exchange parameters. Our results suggest that carrots manage high population density solely through morphological adaptations with no photosynthetic adjustments. Carrot leaves responded to N application in a curvilinear fashion in both cultivars. N did not alter gs, E, or WUE in carrots. N, applied at a rate of 150 kg N ha−1, increased foliar N up to 2.98%. We conclude that 2.98% of foliar N is sufficient to achieve the maximum photosynthetic rates in processing carrots.

Canopy Volume and Root Length Influence Greenshoulder and Internal Greening in Carrot

Greenshoulder (GS) and internal greening (IG) are physiological disorders in carrots that affect root appearance and profits to the producer. Experiments were conducted to examine genotypic sensitivity to GS and IG and to understand the relationship among canopy volume, root length, and GS and IG. Season and genotype affected GS and IG. Genotypes varied in GS and IG significantly and differentially. Regression analysis indicated a significant, negative, linear relationship between leaf area index and GS (R 2 = 0.80, P ≤ 0.0001) and IG (R 2 = 0.62, P ≤ 0.0001), implying that leaf canopy volume influenced the development of GS and IG. There were positive, significant, linear relationships between root length and GS (R 2 = 0.65, P ≤ 0.0001) and IG (R 2 = 0.35, P ≤ 0.0001) development. GS and IG are frequently observed in genotypes that have longer roots. GS and IG can be reduced by optimizing canopy volume.