Plant Growth and Nutritional Quality Attributes of Basella alba Applied with Variable Rates of Nitrogen Fertilizer at Different Planting Dates under Canadian Maritime Climatic Conditions

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.