Submit Manuscript | http://medcraveonline.com Introduction Application of microwave technology in agriculture has gained considerable research attention due to its unique selective heating at the molecular level. 1,2 The electromagnetic wave of microwave irradiation has frequency of approximately 2.45 GHz, which is higher than radio waves but lower than infrared waves. 2 The principle of operation of microwave technology is based on rapid movement of polar (water) molecules leading to collisions and friction that generate localized super heating. 2,3 As such, the quantitative and qualitative effects of microwave irradiation are dependent on various factors such as power output level, exposure time, and the moisture content and heat capacity of the exposed material. These determine heat-load and extent of alteration in the properties of the exposed material. However, the effect of microwave irradiation on the effcacy of compost tea and plant growth performance is unknown. The effcacy and importance of municipal solid waste compost are well documented, especially in improving soil structure, crop productivity and enhancing action transfer. 4–6 Nevertheless, the major concern is the potential release of heavy metals and other solid contaminants from municipal solid waste compost into soils and environment. For that matter, source separation is used to minimize contaminants, 7 while microwave technology was successfully used to extract heavy metals from sewage sludge. 8 It is therefore worthwhile to investigate the use of microwave technology to enhance quality and effcacy of municipal solid waste compost tea while minimizing potential environmental hazards. Plectranthus amboinicus, also known as Jamaican thyme, Mexican mint and others, is popularly used as ornamental, culinary and medicinal plant in the tropics. It is valued for its bioactive compounds for the treatment of fever, skin diseases and control of diabetes mellitus. 9,10 Plectranthus amboinicus is also used for favoring beef, chicken, and goat meats to mask their strong smells. 11 Recent study indicated that vermicompost can enhance growth, antioxidants and anti-Streptococcus properties of Plectranthus amboinicus. 12 Water extracts and infusion of composts are becoming popular foliar spray or soil drench in the agricultural industry. For instance, diluted leachate of vermicompost was used to minimize leaf scorching and other physical damages, and to increase plant growth. 13 Based on these previous studies, it was postulated that an increase in microwave irradiation power output level and time of exposure will enhance compost tea nutrient density to improve plant growth and nutrients uptake. Therefore, the objectives of this study were to determine variations in microwave power level and exposure time alteration of physical and chemical properties of municipal solid waste compost tea, and to assess its impact on Plectranthus amboinicus growth and nutrients uptake. Materials and Methods Location and materials The experiment was performed in the Department of Plant, Food, and Environmental Sciences greenhouse from March to August 2017. Municipal solid waste compost was obtained from Fundy Compost Inc., Brookfeld, NS, Canada. Soft-wood cuttings of Plectranthus amboinicus were obtained from a healthy mother plant in the department’s greenhouse. Promix BX™ soilless potting mix medium (Premier Horticulture Inc., Quakertown, PA, USA) was purchased from a local retailer (Halifax Seeds Company, Debert, NS, Canada). Horticult Int J. 2019;3(4):179‒184. 179 © 2019 Yu et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially. Microwave power level and exposure time alteration of compost tea effcacy, and growth of Plectranthus amboinicus Volume 3 Issue 4 - 2019 Hanchu Yu, Ekene Mark-Anthony Iheshiulo, Lokanadha Rao Gunupuru, Lord Abbey Faculty of Agriculture, Department of Plant, Food, and Environmental Sciences Dalhousie University, Canada Correspondence: Lord Abbey, Faculty of Agriculture, Department of Plant, Food, and Environmental Sciences, Dalhousie University, 50 Pictou Road, Truro B2N 5E3, Nova Scotia, Canada, Email , Received: July 19, 2019 | Published: July 23, 2019 Abstract The unique properties of selective heating at the molecular level, and the resultant enhancement effect of microwave in agri-food sciences have been amply demonstrated. This study examined variations in microwave irradiation power level (0, 100, 200, 300 and 400 W) and exposure times (5 and 10 min) effects on the potency of municipal solid waste (MSW) compost tea and Plectranthus amboinicus plant growth and nutrient composition. A linear regression equation showed slopes of 0.160 o C/W for the 10 min exposure and 0.114 o C/W for the 5 min exposure. The turbidity of the microwaved compost tea reduced as the microwave power level and exposure increased. Electric conductivity, total dissolved solids and salinity of the MSW compost tea increased by a factor of 0.08 at the 400 W power level. Plant sap o Brix, nitrate and calcium concentrations were increased by power levels of ≥300 W. Stem diameter was increased by an average factor of 0.08 for the 5 min and 10 min exposure times following application of the 300 W microwaved MSW compost tea. Chlorophyll content rose by a factor of 0.09 at 10 mins between the 200 W and the 300 W after which it remained unchanged. On the other hand, anthocyanin content was consistently higher in plants treated with the 5 mins microwaved MSW compost tea compared to the 10 mins treatment irrespective of the microwave power level. To understand the mechanism of action of microwaved vermicast, current study is focused on microbial communities in MSW compost tea. Keywords: microwave irradiation, compost, organic amendment, Plectranthus, plant nutrition Horticulture International Journal Research Article Open Access