Development of a Greenhouse Steam-powered, Self-propelled Soil Sterilization Device

This study aims to develop an eco-friendly, self-propelled device to sterilize greenhouses soils with pressurized, superheated steam. The innovated device sterilizes greenhouse soils directly without removing their structures. The device operates electrically with remote control and is equipped with a smart electronic system to control superheated steam temperatures. The device is an alternative to pollutant chemical and long-term solarization sterilization methods. Three forward speeds (steaming exposure periods) of the steam soil sterilizer were tested: 0.05 m s-1 (7s), 0.12 m s-1 (4s), and 0.19 (3s) m s-1. Three pressurized superheated steam temperatures of 153 ºC (0.414 MPa), 170 ºC (0.689 MPa), and 183 ºC (0.965 MPa) were tested at three heights of the steam distributor above the soil surface: 0, 25, and 50 mm. The efficiency of controlling common fungal pathogens, nematodes, and weed seeds were estimated and compared to solarization control. The performance rates, field efficiency, and operating costs of the steam sterilizer were evaluated. The maximal control efficiencies for fungal pathogens for Fusarium oxysporum, Rhizoctonia solani, and Pythium spp. were 90.90, 92.72, and 91.37%, respectively. The highest value of nematode control efficiency was 97.73%. The maximal specific energy consumption rate was 30.96 kW h ha-1 at a field capacity of 0.05 ha h-1 with an average operational cost of 434.18 USD ha-1. The cucumber yield for experimental greenhouses increases by 3.36% over control. It could be recommended to generalize using the developed sterilizer technique in greenhouses for cultivating organic crops.