Irrigation influence on the microclimate of a Mediterranean plastic greenhouse with black mulch and without crop

This work analyses how irrigation affected the microclimate of an unheated plastic greenhouse (South-East Spain) with a typical 'enarenado' soil covered with black plastic mulch and without crop.The greenhouse was divided in two equal compartments, one irrigated and the other non-irrigated.Vents were closed over the entire observation period.Measurements of soil temperature and soil heat flux were conducted throughout the main soil layers for a 9-days period (4-12 April). Temperatures of plastic mulch and air near the ground surface were also measured. Daily integrals of soil heat flux at the gravel-sand mulch and the middle of the imported loamy soil layer were higher in the irrigated greenhouse compartment than in the non-irrigated. Higher soil temperature increments were also found in the gravel-sand layer of the irrigated compartment, compared to the non-irrigated one, but the opposite occurred in the imported loamy soil layer. Plastic mulch temperatures were higher in the irrigated greenhouse compartment at nighttime and morning hours. These differences might be due to higher temperatures at the upper part of the gravel-sand layer and to higher rates of water condensation at nighttime on the inner plastic surface of the irrigated greenhouse compartment. No clear differences between treatments were found for the greenhouse air temperature near the ground.