Influence of winter stress and plastic tunnels on yield and quality of spinach, pak choi, radish and carrot

Plastic tunnels are the viable options for the successful production of cold-tolerant vegetables during cold months of the milder climate regions. However, growing vegetables in northern climates can be a challenge because of long and severe winters. Therefore, we conducted a plastic tunnels study on carrot, radish, spinach, and pak choi in northern Wyoming, USA to explore the viability and quality of the vegetable production under winter stress. The objective was to quantify the effect of different season extension methods on the produce yield, its total phenol content, and antioxidant activity. The experiment consisted of three tunnel systems: high tunnel (Ht), low tunnel (Lt), and low tunnel within high tunnel (LtHt). We were able to harvest vegetables in the freezing November of Wyoming. Spinach, and pak choi had markedly higher yield in LtHt (6,410 kg ha^-1 spinach and 20,644 kg ha^-1 pak choi) than Ht (4,574 kg ha^-1 for spinach and 12,076 kg ha^-1 for pak choi) and Lt (3,253 kg ha^-1 spinach and 8,242 kg ha^-1 pak choi). The concentrations of nutrients in the vegetables weren't affected by the tunnel systems. Greater antioxidant activity of pak choi was evident in Ht than in Lt and LtHt. This experiment demonstrated that challenges of severe winter for growing cool-season vegetables can be mitigated largely by opting for LtHt rather than Lt or Ht alone.