The Costs and Benefits of Sensor Networks for a Cut-flower Greenhouse Operation

Continuous cut flower production of snapdragons (Antirrhinum sp.) requires substantial inputs of energy and resources.  The use of wireless sensor networks can benefit growers by cost reductions achieved through input reductions and potentially by reducing time to harvest and improving quality.  Input reductions also have environmental value by reducing water and nutrient runoff and relieving pressure on scarce water supplies.  We worked with a hydroponic wholesale snapdragon grower in Maryland to install a Decagon (Pullman, WA) wireless sensor network.   Initially, substrate moisture levels were monitored, which provided information that was used to adjust irrigation flows.  A second stage of the project added automated irrigation control to moisture status monitoring.  The grower kept detailed records of production activities, including seed sowing dates and quantities, transplant dates and quantities, harvest dates and quantities, flower quality, and expenditures on energy and labor.  We analyzed those records statistically to estimate changes in productivity, cost, and profitability from the use of the wireless sensor network in both phases of the project.  Preliminary results indicate that the use of sensors reduced minimum time to harvest by 15% to 35%, median time to harvest by 10% to 20%, and maximum time to harvest by 5% to 10%.  The use of sensors also resulted in improved flower quality and lower energy costs.  We use the results of these statistical analyses to estimate the profitability of investing in a wireless sensor network in operations of this kind.