The Use of Shade Cloth and Passive Venting to Delay Spring Bolting in Organic Kentucky High Tunnels

High tunnel technology has allowed season extension and year-round vegetable production for organic producers in Kentucky. The adoption of high tunnels into current production systems has accelerated and numerous organic producers are moving to this production system due to the introduction of NRCS’s Environmental Quality Incentives Program (EQUIP). However, numerous problems concerning the efficiencies and profitability of high tunnels have arisen and limited the productivity of these systems. In response to these questions Kentucky State University completed construction of four gothic-style single-bay high tunnels (30’ by 96’) in 2014. During April and May, heat buildup and light levels in high tunnels can limit profitability by causing lettuces and mustards to bolt. To reduce this effect and delay bolting, a low-cost and energy-efficient strategy using shade cloth and venting was introduced into the high tunnels.  Initial findings during Spring 2014 revealed that the use of 50% light transmission shade cloth with passive venting delayed bolting by 14 days. This delay in bolting allowed for an additional 2 weeks of harvest that would allow producers, on average, an additional $275 in sales per week for each tunnel. Costs associated with installation of the shade cloth and setup of the venting was negligible. Total costs of shade cloth was $160 per tunnel and it is expected that the shade cloth with proper care will last 4 to 5 years. Overall, the total cost of $70 per tunnel each spring for the installation of shade cloth and setup of passive venting makes these management practices economically viable when the potential return is $550.