生物炭对杉木人工林土壤磷素吸附解吸特性的影响

为了改善磷素吸附作用,提高磷在杉木人工林土壤中的利用率,又防止解吸过度引起土壤磷素淋溶造成资源浪费,以杉木树叶和树干为原料,分别在300℃和600℃下制备4种生物炭:300℃杉叶炭(BL300)、600℃杉叶炭(BL600)、300℃木屑炭(BW300)和600℃木屑炭(BW600),分别向土壤中加入0%、2%、4%、8%比例的生物炭,完成吸附解吸试验。结果表明,制备原料和温度对生物炭的成分和性质有决定性的作用,杉叶生物炭pH值、灰分含量、有效磷等的含量显著高于木屑生物炭,且高温炭大于低温炭,其中BL600生物炭pH值、灰分含量及有效磷含量最高;Langmuir模型能很好地拟合生物炭添加后红壤磷素的吸附过程,在低磷浓度时生物炭添加对土壤磷素吸附作用的影响不大,高磷浓度时则促进吸附作用;其中杉叶炭促进土壤磷素吸附的作用大于木屑炭,高温炭大于低温炭,2%和4%的生物炭添加量促进土壤磷素吸附,但8%的添加量会降低土壤对磷的吸附作用;生物炭添加在一定程度上降低了土壤磷素的解吸率,其中木屑炭降低的作用大于杉叶炭;因此建议在磷浓度较高的杉木林人工土壤中添加中低量的BL600,在磷浓度较低的杉木林人工土壤中添加大量的BL600,土壤富磷时能够增强吸附作用,减小土壤磷素淋溶风险,土壤缺磷时增加解吸率来提高土壤磷素利用率。

Effects of Biochar on Phosphorus Adsorption and Desorption Characteristics of Cunninghamia lanceolata Plantation

In order to alleviate the adsorption of phosphorus,increase the utilization rate of phosphorus in the soil of Chinese fir plantation,and prevent the waste of resources caused by the excessive desorption of phosphorus in the soil,in this study,the leaves and wood of Chinese fir were used as raw materials to prepare different types of biochar:BL300 (prepared at the temperature of 300℃ with the fir leaves),BL600 (600℃ with the fir leaves),BW300 (300℃ with wood chips),BW 600 (600℃ with wood chips).The adsorption and desorption experiments were completed by adding 0%,2%,4% and 8% biochar to the soil in turn.The study found that the preparation of raw materials and temperature had a decisive effect on the composition and properties of biochar.In terms of pH,ash content and available phosphorus content of Chinese fir leaf biochar were significantly higher than those of Chinese fir wood chip biochar,and high temperature biochar was higher than low temperature biochar,in which BL600 had the highest pH,ash content and available phosphorus content.Langmuir model could well fit the adsorption process of phosphorus in red soil after biochar was applied.The effect of biochar addition on phosphorus adsorption was not obvious at low phosphorus concentration,but it was promoted at high phosphorus concentration.The effect of Chinese fir leaf biochar on soil phosphorus adsorption was greater than that of Chinese fir wood chip biochar,high temperature biochar was higher than low temperature biochar,and 2% and 4% biochar addition promoted soil phosphorus adsorption,but 8% biochar addition will reduce the adsorption of phosphorus in the soil.The addition of biochar would reduce the desorption rate of soil phosphorus to a certain extent,and the effect of reduction of Chinese fir wood chip biochar was greater than that of Chinese fir leaf biochar.Therefore,it was suggested that low to medium amounts of BL600 be added to the soils of Chinese fir plantations with high phosphorus concentration and large amount of BL600 be added to the soils of Chinese fir plantations with lower phosphorus concentration.When the soil was rich in phosphorus,it could enhance the adsorption and reduce the risk of soil phosphorus leaching.When the soil was deficient in phosphorus,it could increase the desorption rate to improve the utilization rate of soil phosphorus.