Rapeseed cake （RC）, the residue of rapeseed oil extraction, is effective for improving tea （Camellia sinensis） quality, especially taste and aroma, but it has limited ability to ameliorate strongly acidic soil. In order to improve the liming potential of RC, alkaline slag （AS）, the by-product of recovery of sodium carbonate, was incorporated. Combined effects of different levels of RC and AS on ameliorating acidic soil from a tea garden were investigated. Laboratory incubations showed that combined use of AS and RC was an effective method to reduce soil exchangeable acidity and A1 saturation and increase base saturation, but not necessarily for soil pH adjustment. The release of alkalinity from the combined amendments and the mineralization of organic nitrogen increased soil pH initially, but then soil pH decreased due to nitrifications. Various degrees of nitrification were correlated with the interaction of different Ca levels, pH and N contents. When RC was applied at low levels, high Ca levels from AS repressed soil nitrification, resulting in smaller pH fluctuations. In contrast, high AS stimulated soil nitrification, when RC was applied at high levels, and resulted in a large pH decrease. Based on the optimum pH for tea production and quality, high ratios of AS to RC were indicated for soil acidity amelioration, and 8.0 g kg-1 and less than 2.5 g kg-1 were indicated for AS and RC, respectively. Further, field studies are needed to investigate the variables of combined amendments.
WANG LeiYANG Xing-LunK. RACHELWANG YuTONG De-LiYE MaoJIANG Xin
A two-liquid-phase （TLP） soil slurry system was employed to quantify the efficiencies of autoclaving and mercuric chloride sterilization in the dissipation of polycyclic aromatic hydrocaxbons （PAHs）. The fates of 11 PAHs （naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo（a）anthracene, benzo（a）pyrene, benzo（b）fluoranthene, benzo（k）fluoranthene, dibenzo（a, h）anthracene） were recorded over 113 days of incubation. No microorganisms were detected in the HgC12-sterilized soil slurries during the whole incubation period, indicating very effective sterilization. However, about 2% 36% losses of PAHs were observed in the HgCl2- sterilized slurry. In contrast to the HgCl2-sterilized soil slurry, some microorganisms survived in the autoclaved soil slurries. Moreover, significant biodegradiation of 6 PAHs （naphthalene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene） was observed in the autoclaved soil slurries. This indicated that biodegradation results of PAHs in the soil slurries, calculated on basis of the autoclaved control, would be underestimated. It could be concluded that the sterilization efficiency and effectiveness of HgCl2 on soil slurry was much higher than those of autoclaving at 121 ℃ for 45 rain.
WANG Cong-YingWANG FangWANG TaoYANG Xing-LunBIAN Yong-RongF. O. KENGARALI Zeng-BoJIANG Xin
