生物炭对土壤氮素淋失的抑制作用

Effect of Biochar Amendment on Nitrogen Leaching in Soil

淋洗作用是土壤氮肥损失途径之一,也是环境水体氮素污染的重要途径。研发降低土壤氮素淋失的技术途径不仅有助于提高氮肥利用率和降低化肥的施用量,而且有助于防治水体污染和改善生态环境。本文通过淋滤实验研究了生物炭对我国两种重要土壤类型黒钙土和紫色土氮素淋失的影响。由玉米秸秆制成的生物炭按10 t/ha,50 t/ha,100 t/ha的比例施用于土壤,同时模拟田间尿素施用量240 kg.N/ha并用相当于每天10 mm的降水量用去离子水淋洗土壤。对淋滤液氮素组成和含量分析结果显示,在不施用生物炭的条件下,黒钙土和紫色土总氮的淋失量分别占土壤(土壤+尿素)总氮含量的7.5%和9.0%,氮素的淋失主要发生在前130 mm降水过程中,其淋失量占全部淋失量的96%。在淋失的成分中,除硝态氮外,有机氮也是重要的组成物质,二者均占淋失总氮量的48%。生物炭的施用可以大幅度地降低氮素的淋失作用。50 t/ha和100t/ha的生物炭施用量降低黑钙土氮素淋失分别为29%和74%,减少紫色土氮素淋失分别达41%和78%。但10 t/ha的生物炭施用量却增加黒钙土和紫色土氮素淋失量分别达到22%和2%。这表明较低的生物炭施用量会促进氮素的淋失。生物炭对有机氮淋失的抑制作用大于硝态氮。100 t/ha的生物炭施用量对有机氮和硝态氮淋失的降低率分别为88%和62%左右,因土壤类型不同而有所差异。上述研究结果为寻求防治土壤氮素淋失的技术方法提供了理论依据。

Leaching loss is a factor leading to nutrient depletion in soil,and also a major approach to the eutrophication of aquatic environments.How to slow down the nutrient loss in soils is to improve the utilization efficiency of chemical fertilizers,but also to prevent water environments from being polluted.The effect of Biochar on nitrogen leaching was examined in this study by amending the Chernozem and Purplish soils with charcoal from corn stover.The charcoal was mixed in soils at the equivalent rate of 10 t/ha,50 t/ha and 100 t/ha,urea was applied in the top soil at the rate of 240kg N/ha.The soil treatments were watered at the increment of 10mm precipitation everyday.The analyses of the leachate showed that the leaching loss of total N in the control treatment accounts for 7.5% and 9.0% of the N inventories in the Chernozem and Purplish soils,respectively.The loss occurred predominantly in the first 130mm precipitation,and the leachate was composed mainly of organic N and nitrate N,each of which constitutes 48%.Biochar application can reduce the leaching loss significantly.The loss of total nitrogen in the Chernozem was reduced by 29% and 74% at 50 t/ha and 100 t/ha application rate,respectively,while 41% and 78%,respectively,in the Purplish soil.The loss was enhanced,however,at 10 t/ha application rate by 22% and 2% in the Chernozem and Purplish soils,respectively,suggesting that the low application rate of charcoal will exacerbate N leaching.The amelioration effect of charcoal on the leaching of organic N is stronger than that on the leaching of nitrate-N,by 88% vs 62% on average at 100 t/ha application rate.These results provided the basis for developing technologies to prevent the leaching loss of soil nitrogen.