Ng, Betsy Ling Ling

This research study investigated the effects of three differential fertilser treatments on the growth of bermudagrass Tifdwarf (Cynodon dactylon and Cynodon transvaalensis) over a period of ten weeks. Parameters of the study include field capacity, root count, shoot density, hot-water extractable carbon (HWC), microbial DNA concentrations and DNA fragments analysis. They were examined for their usefulness as indicators for soil quality and turf growth. Indicators responding to environmental changes provide invaluable information on the sustainability of a turf. Weekly applications of the organic fertiliser, inorganic fertiliser and Azospirillum biofertiliser (Vital N^TM, Philippines) were given to three individual troughs planted with Tifdwarf. The nitrogen contents in all fertiliser treatments were adjusted to the same level. The effects of the application of organic and inorganic fertilisers were compared and organic treatment notably enhanced the turf density and growth, but not the turf colour. The effects of the application of Azospirillum biofertiliser were compared to the inorganic fertiliser treatment and it was proven that Azospirillum biofertiliser has superior effects on the turf colour, density and growth. These beneficial effects seen were probably due to the nitrogen fixation property of Azospirillum as well as its auxin effect on root growth, thereby increasing the root surface area and uptake of nutrients. HWC is a sensitive measurement for determining impacts of fertilisation and detecting changes in soil organic matter. Organic fertiliser and Azospirillum biofertiliser treatments showed trends of increasing HWC levels. Increased HWC levels would indicate high microbial turnover and high accumulation rate of organic matter. Fluctuations in the microbial DNA concentrations of all treatments revealed the dynamic microbial changes in the soil-plant ecosystem. Microbial shift in soil was greatly influenced by the environmental changes and nutrient resources. The bioavailability of HWC, nutrients, water and other environmental factors impose stress to the ecosystem which can affect the size of microbial pool and diversity, as well as the plant growth. Internal transcribed spacer (ITS) of the extracted microbial DNA was amplified as ITS sequence length varies among microbial species. The microbial DNA profiling through fragment analysis of the microbial ITS sequence among these three treatments showed a dynamic microbial community. The DNA profiling method through the use of fragment analysis reveals the diversity pattern in soil microbial communities. This method has the potential to be used for monitoring soil microbial diversity, which can be correlated to plant growth.