Effect of Amendments of Phosphogypsum and Brown Sugar on Earthworms Ameliorating Coastal Saline Soil
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Supported by the Special Fund for Forest Scientific Research in the Public Welfare (No. 201504205) and the Graduate Training and Development Program of Beijing Municipal Commission of Education of China (Nos. BLCXY201603, BLCXY201604)

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    Abstract:

    【Objective】 Coastal soils in North China are extremely susceptible to salinization because of the geographical and meteorological conditions of these areas. Nowadays, soil bioremediation has proved to be an effective and economical way to ameliorate saline soils and hence been extensively applied. However, researches in this aspect are mostly focused on phytoremediation by planting salt-tolerant plants, and little has been done on use of earthworms or other soil animals. The first phase of this study demonstrates that the introduction of earthworms Eisenia fetida using composted green waste as its food source could help lower salinity of the coastal saline soil in North China. 【Method】 In order to improve the efficiency of using E. fetida and composted green waste to ameliorate saline soil, a field experiment was conducted on addition of phosphogypsum, the conventional soil amendment, and brown sugar in an attempt to determine whether they may help improve the efficiency of the bioremediation. The experimental site was located on a tract of typical coastal saline soil in the Lingang Economic and Technological Development Zone of Cangzhou, Hebei, China. The field was divided into plots. Each plot, covering an area of 12 m2, was amended with 6.5 kg m-2 of composted green waste and earthworms at 50 individuals per m2 (average weight 0.334 g). In addition, the plots were applied with 0 kg m-2, 1 kg m-2, 2 kg m-2, or 3 kg m-2 of phosphogypsum, along with 0 kg m-2, 0.2 kg m-2, 0.4 kg m-2, or 0.6 kg m-2 of brown sugar, separately. 【Result】 The experiment went on for one year, with results showing that the addition of phosphogypsum could significantly decrease pH of the soil in the treatments applied with the same rate of brown sugar, however, the effect did not vary much with the amendment rate of phosphogypsum. As Ca2﹢ and SO42- are the major component of phosphogypsum, application of the substance significantly increased the content of soluble Ca2﹢ and SO42- in the soils the same in brown sugar treatment. The Ca2﹢ in phosphogypsum helped formation of soil structure and promoted desalination of the saline soil, while reducing the content of soluble Na and Cl- significantly; the amendment of brown sugar stimulated activities of the earthworms, thus facilitating formation of soil aggregates and hence leaching of salts, and eventually intensifying the effect of bioremediation. So in the treatments the same in phosphogypsum amendment rate, addition of brown sugar significantly lowered the content of soluble Na and Cl- in the soil. As affected by the contents of soluble Ca2﹢, SO42-, Na and Cl- in the soil, in the treatments amended with 0 kg m-2 or 1 kg m-2 of phosphogypsum, addition of brown sugar significantly lowered the content of total salt, but the effect did not vary with its amendment rate; however, in the treatments the same in the amendment rate of brown sugar, the content of total salt in the soil increased rather than decreased if too much phosphogypsum was used. 【Conclusion】 Aiming at lowering the content of total salt, it is recommended that in addition to 6.5 kg m-2 of composted green waste and 50 individuals per m2 of E. fetida, 1 kg m-2 of phosphogypsum and 0.4 kg m-2 of brown sugar should be amended in bioremediation of the coastal saline soil in North China. Compared with CK (nothing amended), the amendment of composted green waste and E. fetida significantly decreased the content of total salt, and the effect was further enhanced when phosphogypsum and brown sugar was added at a recommended rate. The cost of soil amelioration with the above-described method is only 10.60 Yuan per m2, and it would be lowered if brown sugar is replaced by some by-products from the sugar industry, such as beet pulp, bagasse, and molasses.

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ZHANG Tao, LI Suyan, SUN Xiangyang, WANG Zhenyu, ZHANG Yang, ZHANG Le, GONG Xiaoqiang, ZHAO Xiufang, XIE Zhiyuan, SONG Guoxiang. Effect of Amendments of Phosphogypsum and Brown Sugar on Earthworms Ameliorating Coastal Saline Soil[J]. Acta Pedologica Sinica,2017,54(1):255-264.

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History
  • Received:December 10,2015
  • Revised:September 22,2016
  • Adopted:October 12,2016
  • Online: October 17,2016
  • Published: