Impact of mulch on water loss from a container substrate and native soil

Arboriculture & Urban Forestry: 38 (1): 18-23

This study was designed to measure evaporation from substrate-filled and soil-filled containers (360 L) to simulate a planted root ball. There was no difference in evaporation between mulched and non-mulched soil-filled lysimeters in any consecutive three-day period following irrigation. In contrast, more evaporation occurred the first dry day after irrigation from substrate-filled lysimeters covered with mulch than from those without mulch. Non-mulched substrate-filled lysimeters lost more water to evaporation than mulched lysimeters in the second day after irrigation. Cumulative evaporation through day two was identical for mulched and non-mulched substrate treatments. Cumulative evaporation through the third dry day, after irrigation, was 0.5 L greater from non-mulched lysimeters because of higher evaporation. Mulched or not, only about one liter evaporated daily from the surface of the substrate-filled or soil-filled lysimeters during consecutive, three-day rain-free periods following irrigation. Evaporation accounted for an estimated 4% of water loss from the root ball the first three days following irrigation; based on similar stud - ies with trees present, the remaining 96% would have been lost through transpiration. Given minor reduction in evaporation, and reported disadvantages of mulch application close to the trunk, landscape managers might consider changing mulch application practices for newly planted trees.