Semi-extensive green roof substrate type and depth effects on Zoysia matrella ‘Zeon’ growth and drought tolerance under different irrigation regimes

Abstract

Turfgrass use in semi-extensive green roofs might provide an additional solution for establishing green roofs in urban city centres. The aim of the present study was: (a) to investigate the effects of two extensive green roof substrates formulated from mixing locally available materials with two different organic amendments (peat and locally produced compost) in volumetric proportions as indicated by their subscripts S15:Pum40:Per20:P20:Z5, and S15:Pum40:Per20:C20:Z5 (where S = sandy loam soil, Pum = pumice, Per = perlite, P = peat, Z = zeolite and C = compost), and two substrate depths (7.5 cm or 15 cm) on the growth of Zoysia matrella ‘Zeon’; and (b) to evaluate the effect of various substrate types and depths on the drought tolerance of Z. matrella under two irrigation regimes (3 mm or 6 mm of irrigation every 3 days). The measurements included the determination: (a) of substrate characteristics, and (b) both turfgrass quality and physiological status as indicated by the green turf cover (GTC), normalized difference vegetative index (NDVI) and stomatal resistance. It was found that during the establishment and growth period, the compost-amended substrate improved the GTC compared with those amended with peat. In contrast substrate S15:Pum40:Per20:P20:Z5 improved the drought tolerance of Z. matrella during the drought period compared with the compost-amended substrate. Deeper profiles improved the establishment, growth and drought tolerance of turfgrass compared with the shallower profiles. All three factors (substrate type and depth and irrigation regimes) proved to be influential for turfgrass growth and quality during the drought stress period. During the drought period, the GTC and NDVI were higher and stomatal resistance was lower for the peat-amended substrate, the deeper profiles (15 cm) and the higher irrigation regime (6 mm every 3 days).