Variations in the aluminum fractions within soils associated with different tea varieties (Camellia sinensis L.): Insights at the aggregate scale

Abstract Background Soil aggregates play an important role in the transformation of aluminum (Al) fractions, but little is known about the changes in Al fractions based on the aggregates in soils of different tea varieties. Methods The distribution of Al fractions in aggregates collected from soils planted with four tea varieties (C. sinensis ‘Fuding Dabaicha’ (FD), Chuancha No. 3 (CC3), Chuanmu No. 217 (CM217) and Chuannong Huangyazao (CN)) was investigated by continuous extraction method. Results Results showed significant differences in the distributions of Al fractions among the soils, which were related to the changes in soil aggregate compositions and the aggregate-associated Al fractions. The FD soil had the highest Or-Al concentration, which was related to its high proportion of > 5 mm aggregates and the high Or-Al concentration in the > 5 mm aggregates. The CC3 soil had the highest concentrations of total aluminum (T-Al), water-soluble aluminum (Ws-Al) and exchangeable aluminum (Ex-Al), and the accumulation of T-Al, Ws-Al and Ex-Al depended on the highest concentrations of T-Al, Ws-Al and Ex-Al in the > 5 mm and < 0.25 mm aggregates among the four soils. Therefore, the formation of aggregates and the high Al preservation capacity of the aggregates determined the high Al concentrations of the FD and CC3 soils. Conclusions This study helps elucidate the mechanisms of Al sequestration, and provides evidence for developing appropriate management plans to prevent an increase in Al concentrations in the soils of CC3 and FD by adjusting the soil aggregate composition and the Al concentration of aggregates.