A Brief Study on pH, Exchangeable Ca<sup>2+</sup> and Mg<sup>2+</sup> in Farmlands under Tobacco-Rice Rotation in Xuancheng City of South Anhui

Abstract

pH, exchangeable Ca 2+ and Mg 2+ of soil can influence the yield and quality of flue-cured tobacco. Xuancheng city is the dominant tobacco-planting region in Anhui province since 2008. A general soil survey was conducted in Xuancheng city to understand the current situations of pH, exchangeable Ca 2+ and Mg 2+ of farmlands under tobacco-rice rotation and to decide whether continuous applying dolomite powders to abate soil acidification. In total 124 topsoil samples (0 -20 cm) were collected from the typical farmlands and soil pH, exchangeable Ca 2+ and Mg 2+ were measured. The results showed that soil pH and Ca 2+ and Mg 2+ in Xuancheng city were generally in the suitable grades, pH ranged from 4.56 to 8.42 with an average of 5.87, exchangeable Ca 2+ ranged from 1.01 cmol(1/2Ca 2+ ) kg −1 to 100.55 cmol(1/2Ca 2+ ) kg −1 with an average of 11.07 cmol(1/2Ca 2+ ) kg −1 , and exchangeable Mg 2+ ranged from 0.14 cmol(1/2Mg 2+ ) kg −1 to 2.86 cmol(1/2Mg 2+ ) kg −1 with an average of 0.81 cmol(1/2Mg 2+ ) kg −1 , all spanned from the low grades to the high grades. To the whole Xuancheng city, 37.10%, 62.10% and 72.58% of the surveyed farmlands were in the low grades of pH, exchangeable Ca 2+ and Mg 2+ , respectively, while 52.42%, 25.00% and 20.97% of the farmlands were in the suitable grades, respectively. pH had an extremely significantly positive Napierian logarithm correlation with exchangeable Ca 2+ and an extremely significantly positive power correlation with exchangeable Mg 2+ . In total about 338.2 kg•hm −2 of Ca 2+ and 202.4 kg•hm −2 of Mg 2+ are annually input into the farmlands, while about 110.4 kg•hm −2 of Ca 2+ and 7.4 kg•hm −2 of Mg 2+ are annually moved out from the farmlands, exchangeable Ca 2+ and Mg 2+ were annually increased by 225.2 kg•hm −2 and 187.6 kg•hm −2 in the farmlands, respectively. It

Impacts of earthworm species on soil acidification, Al fractions, and base cation release in a subtropical soil from China

“…Especially significantly higher exchange-able K + , Na + , and Ca 2+ contents of the P. corethrurus casts were observed compared to the control soil (Table 5). It is well known that pH has an extremely significantly positive corre-lation with exchangeable Ca 2+ and Mg 2+ (Wang et al 2018). On one hand, the exchangeable base cation release in earth-worm casts in this study may result in the increase of soil pH values (Kunito et al 2016).…”