High Quality Yield in Lettuce in Response to Low Nitrate Content can be Achieved by Reduced Nitrogen Application
A nitrogen starvation trial was performed using nitrogen-free Yamazaki Solution. A solution culture trial using 100, 95, 90, 85, and 80% full nitrogen strength Yamazaki Solution and a pot trial at nitrogen rates of 0.60 (N1), 0.55 (N2), 0.50 (N3), 0.45 (N4), and 0.40 (N5) g N kg−1 soil were performed to investigate the balance between low nitrate content and quality fresh yield of lettuce (Lactuca sativa L.). The results showed that vacuolar nitrate activity was much higher than cytoplasmic nitrate activity. As exposure increased from day 1 to day 5 in the nitrogen starvation trial, vacuolar nitrate activity decreased rapidly, in contrast to cytoplasmic nitrate activity, which remained stable and the ratios of root biomass and shoot biomass increased. With a decline in the nitrogen supply, the biomass and nitrate content decreased significantly. Therefore, a balance between low nitrate content and quality fresh yield can be achieved by reducing the normal level of nitrogen fertilizer by 10%.