磷石膏、红糖等对蚯蚓改良滨海盐土的促进作用

Effect of Amendments of Phosphogypsum and Brown Sugar on Earthworms Ameliorating Coastal Saline Soil

前期研究表明,施入园林废弃物作为饵料并投放蚯蚓能够降低滨海盐土盐分。通过田间对比试验,研究同时添加磷石膏和红糖对蚯蚓改良滨海盐土的促进作用。结果表明,在每平方米施入6.5 kg园林废弃物及50条蚯蚓(平均质量0.334 g)的基础上,添加磷石膏能够显著降低土壤pH以及水溶性钠离子(Na^+)和氯离子(Cl^-)的含量,但同时会显著增加土壤水溶性钙离子(Ca^(2+))及硫酸根离子(SO_4^(2-))含量;随着磷石膏施入量的提高,土壤全盐量呈现先降低后升高的趋势。添加红糖能够间接降低盐碱土壤水溶性Na^+和Cl^-的含量以及全盐量,但不同红糖施入量的处理间并无显著差异。根据试验结果,推荐在施入园林废弃物作为饵料并投放蚯蚓的基础上,同时添加1 kg m^(-2)的磷石膏及0.4 kg m^(-2)的红糖,以取得最佳的降盐效果。

【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.