我国南方稻田土壤在长期酸雨淋溶条件下养分淋失严重,不但制约了水稻等农作物的可持续生产,而且造成化肥资源的大量无效施用与水体富营养化的环境威胁.近年来研究表明,生物炭在减少亚马逊流域贫瘠土壤养分淋失方面具有突出效果,然而,关于生物炭对我国南方红壤性稻田土壤的养分保持作用研究报道较少.本实验以近几年在我国南方水域频繁暴发引发严重生态危害的入侵植物凤眼莲为生物质前体,于低温慢热解条件下制备生物炭,通过静态共育与模拟酸雨土柱淋溶,系统解析了凤眼莲生物炭(WBC)对稻田土壤养分的持留效果.结果表明:WBC的施用在有效提高土壤pH和CEC的基础上,能够显著增加土壤全N和速效K含量,但却使有效P含量随共育时间的延长而明显降低.在酸雨淋溶条件下,与对照相比,WBC处理中NH4+-N、NO3-N和有效P淋失总量分别减少8.2％-49.8％,14.3％-76.2％和16.6％-43.3％,而K淋失总量提高16.5％-20.8％,但淋溶后WBC处理土壤中速效K含量仍显著高于对照,这表明淋溶液K浓度的升高主要来源于生物炭中丰富的水溶性K.根据以上研究结果,凤眼莲生物炭的施用在短期(1年)内有助于红壤性稻田土壤中主要矿质元素的保蓄持留,对减控稻田面源N、P流失具有重要作用,但其长期效应仍需定位试验的持续跟踪检测.
Leaching of mineral nutrients from paddy soils is generally serious in southern China,which leads to a substantial loss of fertilizers and prevalence in water.In recent years,biochar application to highly weathered tropical Amazon Basin soils has been shown to enhance soil quality and decrease leaching of nutrients.Little,however,is known about the effect of biochar incorporation on fertility of subtropical red paddy soil.In this study,biochar derived from water hyacinth biomass(WBC) was prepared and its impact on soil nutrients level and acid leaching loss was investigated with 1-12 month incubation followed by column test.The results showed significant increases in soil pH,CEC and total amount of N and available K with WBC addition,but a notable decrease in available P with prolonged incubation time.In column leaching test with simulated acid rain,WBC addition significantly reduced the total leached amount of NH4+-N by 8.2％-49.8％,NO3--N by 14.3％-76.2％,and available P by 16.6％-43.3％.But total leached K was increased by 16.5％-20.8％ which could mainly originate from the enriched water-soluble K in WBC.These results indicate the important potential of WBC in retaining major soil nutrients and reducing their leaching from red paddy soils over one year.But the long-term effect of WBC still needs to be testified by positioning trial.
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