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Carrot (Daucus carota L. var sativus) production in Nova Scotia is challenging as carrots are grown under cool temperatures, rainfed conditions, and in mineral soils usually of low fertility. Growers must rely on fertilizer inputs to optimize yields. Excess application can result in high costs and may lead to soil and environmental problems. There is no up-to-date solidly-based, fertilizer recommendation available for carrot production in Nova Scotia. A greenhouse trial was conducted to identify the critical tissue(s) at various growth stages and optimal tissue nutrient concentrations for yield and quality. This will provide a diagnostic tool for assessing plant nutrient health and the opportunity to correct nutrient deficiencies to prevent yield losses, as well as provide an up-to-date fertilizer recommendation. Dicer carrot seeds, variety Red Core Chatenay were grown in sand culture system that used a gravity-fed drip irrigation system. Nine fertility treatments consisting of a complete 20-20-20 plus micronutrients fertilizer was used to deliver at 0, 50, 100, 150, 200, 250, 300, 350, and 400 ppm equivalent of N, P, and K. Soil and plant tissue samples were taken at 4 and 9 weeks and at final harvest at 13 weeks. Critical tissues varied for each element studied at each of the growth stages. Results suggest 0 and 50 ppm treatments did not provide enough fertilizer to obtain maximum growth while plants receiving above 300 ppm were found to be more susceptible to disease. The treatment with 100 ppm N, P, and K was optimal, being significantly higher in yield and quality than all treatments except 150 ppm.

Increasing temperature as a result of global climate change is expected to exert a great influence on agricultural crops, possibly through effects on photosynthesis. Response to temperature of leaf gas exchange parameters of carrot (Daucus carota L. var. sativus) cultivars Cascade, Carson, Oranza, and Red Core Chantenay (RCC) were examined in a controlled growth room experiment. Leaf net photosynthetic rate (P_N), stomatal conductance (g_s), and transpiration rate (E) were measured at temperatures ranging from 15 to 35 °C at 370 μmol·mol^-1 (CO₂) and 450±20 μmol·m^-2·s^-1 PAR. The cultivars responded similarly to increasing temperature and did not differ in most photosynthetic parameters except g_s. The P_N increased between 20 and 30 °C, thereafter increasing only slightly to 35 °C. On average, increasing temperature from 20 to 30 °C increased P_N by 69%. Carboxylation efficiencies (Ca/Ci ratio) ranged from 1.12–2.33 mmol·mol^-1 while maximum P_N were 3.25, 3.90, 5.49, 4.19 μmol·m^-2·s^-1 for Carson, RCC, Cascade, and Oranza, respectively. The E did not reach maximum at 35 °C while g_s peaked at 30 °C and then decreased by 93% at 35 °C. The water use efficiency (WUE) decreased with an increase in temperature due to increases in both P_N and E. The results indicate that increasing temperatures above the seasonal average (<20 °C) increases both P_N and E up to 30–35 °C. An increase in photosynthesis due to an increase in temperature is expected to hasten growth. Carrots may be able to withstand a moderate increase in temperature.

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 (P_N), stomatal conductance (g_s), 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 P_N, which did not reach saturation. The g_s and E increased to a peak between 600 and 800 &#956;mol·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 P_N until saturation at 650 μmol·mol^-1. The g_s 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 P_N and E. The P_N decrease was cultivar specific. Nutrient concentrations of 0 to 400 ppm gave a similar pattern of decrease for P_N, E, and g_s. Treatment of 50 ppm had the highest P_N, E, and g_s. The WUE generally increased with increasing nutrient concentration.

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.