2013 ASHS Annual Conference

Low cost high tunnels are unheated, structures built from PVC or metal pipe and polyethylene glazing or shade cloth. They provide protection from adverse weather conditions such as rain, snow, wind, and hail and buffer plants from temperatures below freezing. These tunnels are an alternative controlled environmental agriculture structure for growers interested in crop production but without the need for high initial capital investment in greenhouses which contain full automation of their production systems. Currently, there is much interest in small scale, local food production, but many beginning farmers are not aware of the costs of production, which include initial investments for infrastructure, supplies, and labor. The objective of this study is to document the cost of production of leafy vegetables and herbs in low cost high tunnels in the arid Southwest. Two high tunnels with the dimensions of 4.2 m by 12.8 m (14 by 42 feet) were constructed with raised beds at the University of Arizona Campus Agriculture Center in Tucson. Kale (Brassica napus var. pabularia cv. Red Russian), spinach (Spinacia oleraceae cv. Bloomsdale), arugula (Diplotaxis tenuifolia cv. Sylvetta), and cilantro (Coriandrum sativum cv. Santo) were direct seeded in December 2012 in replicated plots in the two high tunnels. Tunnel remained closed for passive heating from solar radiation during seed germination and crop establishment. Air and soil temperatures in the tunnels were recorded and minimum temperatures were –7 °C and 4.5 °C, respectively, while maximum air temperature briefly exceeded 38 °C and soil temperatures reached 17 °C. Mild injury on heat tolerant kale was detected, none of the other crops sustained freeze damage. Harvesting of mature leaves from each crop began 59 days after planting and was repeated when sufficient new leaf material was produced.  Average harvested fresh and dry weight per square meter of production area for the different species were as follows: spinach 580 g and 55 g; kale 758 g and 72 g; arugula 442 g and 49 g; and cilantro 927 g and 118 g. Material costs and time for construction of the high tunnels, preparation of the raised beds, and sowing, maintaining and harvesting crops were documented to estimate construction and labor costs for this type of business. This information will assist beginning farmers in making sound financial decisions when investing in high tunnels.