Nitrogen (N) fertilization at critical planting time is important to optimize productivity and reduce nitrate accumulation in edible portions of green leafy vegetable plants. A field experiment was performed to determine the effects of variations in N rate and planting time on plant growth, yield, and nutritional quality attributes of Basella alba under Atlantic maritime climatic conditions. The N rates were 0 (control), 40 (low), 80 (medium), and 120 kg ha−1 (high) at planting times 15 June–3 August (early season), 6 July–20 August (mid-season), and 4 August–8 September (late season). Plant height, number of branches, and stem girth were increased after 45 days after sowing in early and mid-season plantings, but leaf length decreased during the same time by 32.8% in the late planting. The average yield obtained in early, mid-, and late plantings were 171, 464, and 328 g plant−1, respectively. Low N gave the highest yield in early planting while medium N gave higher yields in mid- and late plantings. However, the medium N increased nitrate accumulation in B. alba by 7% compared to the high N rate. In general, there was no significant effect of N on B. alba total phenolic and total carotenoid contents. Overall, the highest yield was obtained during the warmest summer months of mid- and late plantings. Therefore, there is a potential to grow B. alba as a summer vegetable under Canadian Atlantic maritime conditions. However, it is recommended to reduce the rate of N fertilizer application during high-temperature conditions. Future studies are required to investigate phosphorus and potassium fertilization and nitrate accumulation in B. alba and potential health risks.
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