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.
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机译：菜籽油（RC）是菜籽油提取物的残留物，可有效改善茶树（Camellia sinensis）的品质，尤其是味道和香气，但改善强酸性土壤的能力有限。掺入了碱渣（碳酸钠回收的副产品）。研究了不同含量的RC和AS对茶园酸性土壤的改良效果。实验室温育表明，将AS和RC组合使用是可行的。一种降低土壤可交换酸度和A1饱和度并增加碱饱和度的有效方法，但不一定对土壤pH值进行调节。组合修正剂释放的碱度和有机氮的矿化作用最初使土壤pH升高，但随后由于硝化程度的高低与不同钙水平，pH和氮含量的相互作用相关。 AS抑制土壤硝化作用，导致pH值波动较小。相反，高AS刺激土壤硝化作用时，如果大量施用RC会导致pH值大幅降低。基于茶叶生产和品质的最佳pH值，高比例指示AS至RC可改善土壤酸度，指示AS和RC分别为8.0 g kg-1和小于2.5 g kg-1。此外，还需要进行田间研究以研究组合改良剂的变量。
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