生物质灰对红壤酸度的改良效果

EFFECTS OF BIO-ASH AMELIORATING RED SOIL IN ACIDITY

用采自安徽、浙江、湖南和广东的4种红壤和1种赤红壤,通过室内培养实验研究了添加生物质灰对酸性土壤的改良效果。结果表明,添加生物质灰提高了土壤p H,降低了土壤交换性铝含量,且阳离子交换量(CEC)越小改良效果越明显。改良后土壤交换性K+、Ca2+、Mg2+含量也显著增加,交换性Ca2+增幅最大,其次为交换性K+。有效磷含量也有增加,磷含量较高的土壤有效磷增幅更大。虽然生物质灰含有一定量的重金属,但由于用量较少,对土壤有效态重金属含量的影响小,施用生物质灰的环境风险较小。总之,添加生物质灰不仅可以有效改良红壤酸度,还可提高红壤肥力。

In this study, 4 types of red soils and a lateritic red soil collected from Anhui, Hunan, Zhejiang and Guangdong were used in an indoor incubation experiment to investigate effects of bio-ash ameliorating these soils in acidity. The bio-ash was produced by the burning of poplar skin mixed with rice and wheat straws in a power plant. Results show that application of bio-ash increased soil pH, decreased soil exchangeable Al^3＋. The ameliorating effect of 8 g kg^-1 bio-ash on soil acidity was better than that of 4 g kg^-1 b/o-ash, and the effects were more pronounced when soil cation exchange capacity （ CEC ） was lower. Because the pHs of the five soils were in the range from 4.2 to 5.0 in which soil acidity was buffered by cation exchange reactions, therefore CECs of soils had important influences on ameliorating effect of the bio-ash on soil acidity. The soil with the higher CEC had the greater buffering capacity to acid, thus the pH of the soil was more difficult to be increased. The increase in pH for different soils due to the incorporation of the bio- ash followed the order： the red soil from crop land in Zhejiang 〈the red soil from crop land in Anhui 〈the red soil from osmanthus garden in Zhejiang≈the red soil from crop land in Hunan 〈the lateritic red soil from forest in Guangdong, which was opposite to the changing trend of CECs for these soils. The lateritic red soil from Guangdong with the minimum CEC obtained the greatest increase of soil pH by 1.1 pH units after the bio-ash incorporated; while the maximum CEC of the red soil from crop land in Zhejiang led to the minimum increase in soil pH by 0.59 pH units. The contents of exchangeable K^＋, Ca^2＋ and Mg^2＋ in these acid soils were also significantly increased due to the incorporation of the bio-ash. The soil exchangeable K^＋ was increased by 0.40- 0.63 cmol kg^-1, the exchangeable Ca^2＋ was increased by 1.93 -2.57 cmol kg^-1, and the exchangeable Mg^2＋ was increased by 0.30 - 0.36 cmol kg^-1. Therefore, the effect was the highest with soil exchangeable Ca^2＋ and then soil exchangeable K^＋. The content of available phosphorus also increased in these soils, particular in soils high in P content. Although hio-ash contains a certain amount of heavy metals, the application of bio-ash would not have much impact on contents of available heavy metals in the soil because of its low application rate. Therefore, the environmental risk of bio-ash application in acidic red soils is small. To sum up, application of bio-ash will not only effectively ameliorate red soil in acidity, but also improve red soil in fertility.