Lei WANG Xing-Lun YANG K. RACHEL Yu WANG De-Li TONG Mao YE Xin JIANG. Combined Use of Alkaline Slag and Rapeseed Cake to Ameliorate Soil Acidity in an Acid Tea Garden Soil. Pedosphere 201323(2): 177–184

Abstract

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 Al 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