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  • Author or Editor: Steve Kyei-Boahen x
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Genotypes and environmental parameters interactively act on plants and modify their yield responses through modifying photosynthetic processes. In order to optimize yield, it is critical to understand the photosynthetic behavior of the crop as altered by genotypes and environment. Leaf gas exchange parameters of carrot (Daucus carota L.) cultivars Cascade, Carson, Oranza, and Red Core Chantenay (RCC) were examined in response to various irradiances, fertility levels, moisture regimes, and to elevated CO2 concentrations. Leaf net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were measured. Cultivars responded similarly to increasing PAR and CO2 concentrations and did not differ in photosynthetic parameters. Increasing PAR from 100 to 1000 μmol·m-2·s-1 increased PN, which did not reach saturation. The gs and E increased to a peak between 600 and 800 μmol·m-2·s-1, then rapidly declined, resulting in a sharp increase in water use efficiency (WUE). Increasing CO2 concentrations from 50 to 1050 μmol·mol-1 increased PN until saturation at 650 μmol·mol-1. The gs and E increased to a peak at 350 μmol·mol-1 and then declined. WUE increased linearly with increasing CO2. Carrots exposed to drought over a period of 5 days decreased PN and E. The PN decrease was cultivar specific. Nutrient concentrations of 0 to 400 ppm gave a similar pattern of decrease for PN, E, and gs. Treatment of 50 ppm had the highest PN, E, and gs. The WUE generally increased with increasing nutrient concentration.

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Green shoulder (GS) and Internal Greening (IG) are the physiological disorders in carrots due to chlorophyll accumulates either at the crown or internal tissues or both. GS and IG affect root quality and makes carrot roots unfit for consumption and cause a great lose to the processing industry. One of the hypothesis in our study was that plant population modulate GS and IG due to its variation in light interception. The objectives of this study were to identify the effect of plant population on the occurrence of GS and IG and establish a relationship between them. Dicer (Red core chantenay) and Slicer (Caro choice) varieties were seeded at various seeding rates. The experiment used a Randomized Block design. Each treatment was replicated four times. GS and IG were measured using a Chlorophyll meter and the output was read as Chlorophyll Index (CI). Leaf area index (LAI) was determined using a LAI-2000 Plant canopy analyzer. Carrot roots were also collected per meter for each plot. Plant population showed a significant negative correlation with GS. Correlation also existed between GS and LAI. However, plant population and LAI had poor correlation with IG in both the Dicer as well as in the Slicer varieties. It is possible that the IG may perhaps be induced prior to canopy development. Also, a poor correlation existed between IG and GS in both the Slicers and Dicers implying that one does not control other event.

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A reduction in the atmospheric deposition of sulfur (S) and S-containing fertilizers has greatly reduced S inputs to the soil in recent years. At the same time, S removal from the soil has increased as a result of increased crop production and higher yields. Sulfur deficiency has been found to reduce yields in several crops. A study was conducted to gain an understanding of the S status of Nova Scotia soils that support carrot production, as well as to examine the effects of rate of S application, method of S application, and type of S fertilizer on carrot uptake, distribution, yield, and recovery. Initial S concentrations in carrot-producing fields ranged from 52–440 kg·ha-1 of S. In general, King's County soils were lower in S than Colchester County soils. In the S trial, banding and broadcasting S on the side of carrot rows improved yield, and recovery compared to placing the S in the seed row. Banding S also significantly increased undersize carrots, leaf fresh weight, leaf dry weight, and root fresh weight. Rate of S application did not affect yield, recovery, or growth of carrots. At this time, S supplies from the atmosphere and soil are sufficient to meet the demands of carrots produced for processing in Nova Scotia. Growers do not need to apply S as fertilizer at this time to improve carrot yields. Monitoring of the S status of soils should be periodically conducted to assess S concentration as SO2 emissions and crop production continue to change.

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