Abstract

Under desert climatic conditions in Riyadh, Saudi Arabia, thermal sensation and heat stress were assessed in a plastic greenhouse with and without evaporative cooling. For the evaluation, appropriate thermal comfort and heat stress scales were chosen. In the greenhouse, measurements of the necessary parameters, including the dry and wet bulb temperatures, globe temperature, natural wet bulb temperature, and solar radiation flux, were made during hot, sunny days. The findings indicated that workers in an uncooled greenhouse would experience high heat stress and would feel very uncomfortable for the majority of the day. At night, however, they would not be at danger for heat stress and would feel at ease. When it comes to comfort and reducing heat stress, efficient evaporative cooling is required during the day but not at night. Workers in the cooled greenhouse are free to engage in any activity, with the exception of noon, when they should adhere to a proposed working schedule in which the various tasks were divided up among the daylight hours depending on the heat stress value. The ideal relative humidity and air temperature ranges in greenhouses are 48-55 percent and 24-28°C, respectively, to prevent heat stress and to maintain comfortable conditions.

In greenhouse pepper (Capsicum annuum L.) cultivation, five different substrates with soil (S) and/or MSWC combinations (0-5-10-20-40 percent) utilised with or without fertigation were used, together with municipal solid waste compost (MSWC) and/or fertigation. The growth of the plants rose by 10–20% MSWC, and fertigation primarily improved plant height. In S: MSWC 80: 20, the amount of fruits grew without fertiliser. As MSWC content increased,plant biomass increased as well. Regarding leaf fluoresces and plant yield, there were no variations. The addition of MSWC boosted the substrate's nutritional value (N, K, P, and organic matter), which raised the EC. Fruit fresh weight dropped (up to 31%) as plants were grown in soil with more MSWC. Fruit size varied depending on the amount of MSWC added to the soil, and this had more of an impact on fruit diameter than fruit length. It's interesting to note that the size of marketable fruits shrank as the substrate's MSWC concentration rose, but the addition of fertiliser swung the trend back in the other direction and kept the fruit marketable. Fruit acidity and total phenols were decreased as a result of MSWC, but fruit lightness was increased. There were no variations in the peppers' EC (total coliform and E. coli) and bacteria (fruit dry matter content, fruit firmness, green colour, total soluble sugars, or EC of peppers). Low MSWC level increased plant growth and preserved fruit fresh weight for greenhouse peppers without impacting plant output, although fertigation had a positive effect.