EFFECTS OF WASTE CRUMB RUBBER ON MEDIUM CHARACTERS AND GROWTH OF LOLIUM PERENNE L.

Crumb rubber, a product of waste rubber, may be used in sports turf medium for alleviating soil compaction. Crumb rubbers with diameter of 0.5-1 mm were applied through turfgrass rooting medium at seven scales (0%=control, 6%, 9%, 12%, 15%, 18%, 21%) and the effects of crumb rubber on turf medium characters and growth of Lolium perenne L., were investigated. Crumb rubber improved the properties of sand-based medium such as the decreasing bulk density and increasing water retention. Crumb rubber application didn't affect seed germination of L. perenne significantly as compared to control. In contrast, a significant reduction in shoot length was observed in two stubbles of L. perenne. However, the first stubble in 15% crumb rubber treatment and the second stubble in 12% crumb rubber treatment exhibited better growth and higher shoot length was obtained than other treatments. Addition of varying proportions of crumb rubber also markedly decreased shoot fresh and oven dry biomasses, and the effect was more pronounced at 21% crumb rubber treatment for the second stubble, but 15% crumb rubber gave the highest aboveground biomass for two stubbles among all crumb rubber treatments. There were no significant differences in the root length and fibrous root number between crumb rubber treatments and control except for 21% and 6% treatments. However, crumb rubber had positive effects on root biomass and chlorophyll content of the second stubble. Crumb rubber 15% and 18% increased root biomass by 94% and 108% respectively, relative to control. Maximum increase in chlorophyll content of the second stubble was observed at 18% crumb rubber treatment. The net photosynthetic rate (Pn), stomatal conductance (Gs) was improved at 18% proportion of crumb rubber. The findings of the trial suggested that the optimum proportion of crumb rubber added in L. perenne medium was between 15% and 18%, which would not affect plant growth obviously and may improve some growth parameters.