The effect of microclimate and irrigation intervals on performance of urban landscape plants based on soil moisture measurement

Abstract: In today’s world, the growth of urban and suburban population has increasingly shifted the balance between the water demand and the available water resources. Moreover, the synchronization of maximum consumption of water in urban landscapes with the drinking water sector has caused the landscape to be a serious competitor for urban drinking water sources. This study investigates the effects of environmental variations at two locations (lake complex and city center park in Golbahar, Khorasan Razavi province, Iran), and irrigation intervals at three levels (daily, 2-day and 3-day) on some performance characteristics of urban landscape plants (height, root length, leaf relative water content, proline in lawn and mixed lawn, electrolyte leakage and stomatal conductance in lawn, mixed lawn and mixed tree) based on soil moisture measurements. Sensors were installed after calibration at depths of 0-10 cm for lawn and at depths of 0-10, 10-30 and 30-50 cm for mixed lawn and trees. The highest moisture depletion for lawn was observed in both locations due to the level of evapotranspiration in August, July, and June, respectively. In the city center park, the soil moisture percentage and soil adsorption rate at the time of irrigation as well as the rate of desorption was higher than the lake complex. In mixed lawn and tree pattern, the moisture content of the soil layers decreased with increase of depth, and the maximum desorption occurred in July and August. The effect of microclimate resulted higher lawn height value at the lake complex than the city center park, and there was no difference between the lawn and the mixed lawn. Also, with increase in irrigation interval, the height of lawn was significantly decreased. Moreover, the effect of location of irrigation and irrigation interval on root length was not significant. The relative water content percentage decreased 28 % in three-day irrigation compared to daily irrigation. For proline concentrations, only location and irrigation intervals were significant. The lower levels of electrolyte leakage indicated higher resistance of tree in similar irrigation conditions, which increased 12 percent with increase in irrigation intervals, from 1 to 3-day. The average stomatal conductance in the leaves indicated that it was less for the lawn than the tree in the same irrigation interval due to the greater resistance of the tree to drought against lawn. Upon the results, soil moisture sensors can be used as a tool in irrigation decision making which could contribute to water saving in amenity urban landscapes.