生物炭对菜地土壤氮平衡及酸碱缓冲能力的影响

针对太湖地区菜地化肥氮投入量较大导致氮淋失严重及土壤酸化的现状,选取太湖地区的菜地土壤,利用盆栽试验连续种植三季小白菜,结合生物炭埋袋回收技术,研究不同化肥氮施用量(以N计,0和110 mg/kg)及生物炭添加量(w为0%、1%、2%和5%)对土壤氮淋失及酸碱缓冲能力的影响. 结果表明:在化肥氮施用量为110 mg/kg条件下,与无生物炭添加相比,生物炭添加量为2%时可使作物对土壤矿质态氮的利用效率提高约1倍(由41%增至81%),因化肥氮施用引起的土壤氮素残留量降低83%；生物炭添加可有效减少48%~65%的土壤氮淋失量,当添加量为1%、2%时,生物炭主要通过削减淋失液中ρ(TN)来降低土壤氮淋失量；添加量为5%时,则主要通过削减淋失液体积来实现. 无论是否添加化肥氮,生物炭均能有效维持土壤原有的pH、w(有机质)及w(盐基离子)；促使土壤酸碱缓冲能容量增加22%~37%,致酸速率降低17%~80%,显著提升了土壤的酸碱缓冲能力. 研究显示,在化肥氮施用量为110 mg/kg条件下,生物炭添加量为2%时能对土壤酸化产生较好的缓冲效果. 

Influence of Biochar Addition on Soil Nitrogen Balance and Buffering Capacity for Vegetable Soil

The hypothesis of using biochar to reduce nitrogen input and leaching, improve nitrogen balance and increase buffering capacity on vegetable soil was tested in Lake Taihu region in China. A pot experiment was conducted with completely randomized splitting block design and six replicates with three growing seasons including two levels of chemical nitrogen (urea) input (0 and 110 mg/kg dried soil) and four levels of biochar addition (0%, 1%, 2% and 5% of dried soil). Soil was collected from vegetable fields in Lake Taihu region. Pakchoi (Brassica chinensis) and slightly alkaline biochar were used in the experiment. The results showed that biochar could significantly enhance the nitrogen (N) utilization ratio of pakchoi over 100%, reduce 83% soil N residues from urea application, and decrease 48%-65% N loss from leaching under the urea continuous applied condition. Biochar reduced N leaching loss through lowering the concentrate of nitrogen (ρ(TN)) of leachate at 1% and 2% biochar addition treatments, and through controlling the volume of leachate in 5% biochar addition treatment. The application of biochar increased soil pH buffering capacity by 22%-37% with or without urea addition, slowed down acidification rate by 17%-80%, and maintained soil w(organic matter) and w(base cations). The biochar addition at 2% with application of chemical N (urea) at 110 mg/kg dried soil could be concluded to have positive influence on the improvement of soil buffering capacity; therefore it is recommended for applying in vegetable fields in the Lake Taihu region.