Evaluating the effect of compost application on soil CO₂ level and growth of Cinnamomum Camphora seedlings.

抄録

The call for the conservation of the environment through reduction of waste and promotion of recycling has been gathering strength for a number of years. In Japan, the Fukuoka Greenery Recycling Center was built with the intention of diversifying waste disposal methods and therefore making great contribution towards conserving the environment. The Fukuoka City Government has adopted the practice of amending soil with recycled materials. Two types of compost materials were used and their effects on plants and CO₂ concentration in soil were evaluated. The first type consisted of mixtures of perlite, peat moss and slow decomposing fertilizer (the traditional way of amending soil in Japan) and secondly, the newly developed recycled materials (RC) generated from mixtures of processed garden wastes/tree pruning, waste timber and sewage sludge collected from households. Mixtures of these materials were applied at different rates and application varied at depths of 0 (surface application), 0-25cm, 0-50cm and 0-100cm, with corresponding application concentrations of 100, 30, 15 and 7.5 percent, respectively.

The recycled compost had a positive effect on the growth of Cinnamomum camphora seedlings, particularly when soil was amended with 15 percent concentration (RC15%) applied at 0-50cm-soil layer, and even at lower concentration (7.5 percent) applied at 0-100cm. Among the treatments, RC15% showed significantly higher biomass production, and higher height growth was also observed in RC30% (718.2g and 154.3cm), as compared with the effect of mixtures of perlite, peat moss and slow decomposing fertilizer (200.1g in TC15% and 125.7cm in TC30%).

The observed temporal and spatial variations in soil CO₂ concentrations were attributed mainly to biotic (root respiration and microbial activity) and abiotic (soil temperature and soil moisture content) factors. Observed CO₂ concentrations vary according to time, depth and amount of compost applied. The highest concentration was observed in September 1999 under RC 7.5% (5.30 percent) at 60cm and the lowest during winter (January 1999) with 0.13 percent of the control treatment at 8cm depth. Soil CO₂ concentration has a strong positive correlation with temperature (r=0.95) and is also significantly correlated with moisture content (r=0.63) at 100 cm soil depth. Strong correlations of temperature at any given depth indicate temperature’s significant role in determining the level of CO₂ concentration. Moreover, compost applied to the deeper soil layer at a low concentration (RC 7.5%) greatly affected respiration rates, contributing to a higher CO₂ concentration in the deeper soil layers (40 ~100cm). However, it was found that the observed higher CO₂ concentration had no detrimental effect on the growth of plants studied.