Increasing the productivity and quality of cucumber crop by improving the performance of the evaporative cooling system

Evaporative cooling in the kingdom of Saudi Arabia is one of the most important cooling systems used inside greenhouses to obtain an acceptable temperature change in hot, dry climates. It is considered insufficient during very hot summer periods, when temperatures outside the greenhouse reach approximately 48 degrees C, which affects the efficiency of cooling, and thus, creates stress on the plants, leading to wilting and a decrease in the production rate. The cooling system is developed by making an insulated rectangular tunnel. The air comes out through vertical openings directly to the plants. The results of evaluating plant heat stress in the developed cooling system (DCS) showed an increase in the values of the photosynthesis rate, transpiration rate, carbon dioxide exchange, and stomatal conductance. The plants also appeared well in terms of the shape of the leaves, their freshness, the abundance of flowers, and the large size of the fruits, while in the traditional cooling system (TCS) the plants exhibited some wilting and some brown spots. The hectare yield reached 42.49 ton/ha for the DCS system, while it reached 37.53 ton/ha for the TCS with an increasing rate of 13.22 %. The total weight of fruits harvested within 60 days of cultivation was 4.25 kg/m(2) for the DCS and 3.75 kg/m(2) for the TCS. The dry and fresh weight of fruit, stem, and leaves, total dissolved solids, vitamin C, chlorophyll percentage in leaves, and total plant acidity, were higher in DCS compared to the TCS.