Effects of urea-N and CO2 coupling fertilization on the growth, photosynthesis, yield and anthocyanin content of hydroponic purple cabbage Brassica campestris ssp. Chinensis

Abstract

Water and fertilizer coupling is a high-efficiency technology for the development of facility agriculture. However, the interaction effect of nitrogen (N) and air carbon dioxide (CO 2 ) on hydroponic purple cabbage, especially on its leaf anthocyanins under hydroponic solution systems, remains unexplored. In this study, six treatments were set as C0N0, C0N2, C0N4, C1N0, C1N2 and C1N4, with N0, N2 and N4 being 0.0 g/L, 0.2 g/L and 0.4 g/L exogenous urea-N to hydroponic solution dilution, respectively. C0 and C1 were set as with and without CO 2 fertilizer (i.e., 800 g CO 2 agent added one week after transplanting and 600 g CO 2 agent added when the plant reached 15 cm in height), respectively. Pot experiments were conducted to investigate the interaction effect of N and air CO 2 (N×CO 2 ) on the growth, photosynthesis, yield and anthocyanin content of hydroponic purple cabbage Brassica campestris ssp. chinensis. The results showed N×CO 2 extremely significantly influenced plant height (H), net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular oxidation concentration (Ci), transpiration rate (Tr), leaf water use efficiency (LWUE) and yield. The C1N0 treatment had the largest yield at 262.5 g/plant, with higher values for root length, root weight, plant height and leaf number than the other treatments. The Pn, Ci and Tr of C1N4 were the highest at 3.05 μmol CO 2 /m 2 •s, 352.8 μmol CO 2 /m 2 •s and 2.31 mmol H 2 O/m 2 •s, respectively. The C1N2 treatment received the largest Gs value of 0.70 mol H 2 O/m 2 •s and the largest Tr of 2.31 mmol H 2 O/m 2 •s. There was the highest LWUE for C0N2 (1.41) and the highest anthocyanin content for C1N2 (1.35 mg/kg). There was a significant negative correlation between leaf number and anthocyanin (r = -0.414, p<0.05). The findings demonstrated that adding CO 2 fertilizer and 0.2 g/L exogenous urea-N to hydroponic solution dilution is a potential N×CO 2 coupling strategy to increase anthocyanin and the yield of purple cabbage.

Effects of biofertilizer and water-saving irrigation interactions on the leaf photosynthesis and plant growth of tomatoes

“…High quality, efficient and intelligent cultivation of tomatoes is a current research hotspot, whereas it also faces problems such as low irrigation and fertilizer utilization and environmental pollution. Irrigation and fertilizer directly influence tomato growth and development, yield formation and fruit quality [4][5][6] . Optimizing irrigation and fertilizer management helps to sustain greenhouse tomato production, achieve the "win-win" strategy of high yield and profit maximization, and reduce environmental risks caused by irrational fertilization management practices [7] .…”