芦荻生物质炭基肥研制及其对水稻土氮损失的影响

为实现秸秆资源化利用和强化生物质炭基肥生产应用,以洞庭湖芦荻秸秆热解生物质炭为基质,采用包膜和混合造粒技术,以改性淀粉为黏合剂,辅以膨润土、腐殖酸等材料制备包膜炭基肥(CT)和混合炭基肥(MT)。以生物质炭占比10%(T1),15%(T2),20%(T3),25%(T4)和30%(T5),从微观形态结构、养分释放速率、粒径及抗压强度等基本性质进行择优筛选,将筛选后的炭基肥处理(CT2、CT3、CT4和MT1、MT2、MT3)与普通复合肥(NPK)、不施肥(CK)共8个处理进行室内水稻盆栽试验,对比不同研制方式及生物质炭添加量下水稻土氨挥发及氮素渗漏流失差异。结果表明:炭肥比越大,肥料结构愈紧密,累积氮素释放率愈低,但过量的生物质炭的添加会造成肥料粒径不均匀、抗压强度不达标。包膜生物质炭基肥以15%~25%的生物质炭添加量较适宜;混合生物质炭基肥以10%~20%的生物质炭添加量较适宜。与NPK处理相比,CT2、CT3、CT4处理氨累积挥发量分别降低12.95%,27.96%,23.82%,氨挥发损失率分别降低16.56%,35.67%,30.57%,以CT3效果最好;MT1、MT2、MT3处理氨累积挥发量分别降低33.72%,41.48%,16.06%,氨挥发损失率分别降低43.31%,53.18%,20.38%,以MT2效果最好。2种炭基肥均可减少盆面水铵氮平均浓度,与NPK处理相比,最高降幅分别达20.74%(CT4)和39.90%(MT2);混合造粒炭基肥中以MT2处理的全氮、硝氮浓度降幅最大,分别达5.50%,5.09%,而包膜炭基肥各处理间差异均不显著。与NPK处理相比,施包膜炭基肥处理的渗漏水中铵氮与全氮平均浓度分别显著降低8.93%~14.00%,8.84%~16.38%,而各处理间硝氮平均浓度均无显著性差异。施混合炭基肥可降低铵氮、硝氮和全氮平均浓度,分别达11.16%~12.42%,3.22%~22.29%,11.14%~15.86%。此外,炭肥比越高,生物质炭的氮减排效应越明显,但添加量过大其氮减排量并无显著性增加。总体而言,2种工艺制备生物质炭基肥均能有效降低氨挥发损失以及减缓氮素径流渗漏损失风险。其中,包膜炭基肥以20%~25%生物炭添加量效果最优,混合炭基肥以15%最优。

Effects of Biochar Fertilizers Prepared by Reeds with Different Techniques on Nitrogen Loss in Paddy Soil

For the dual purposes of the straw resource utilization and strengthening the biomass carbon basal application, the rushes straw in the Dongting Lake was pyrolysised as biomass substrate. Using the coated and mix granulation technologies, the coated (CT) and mixed (MT) biochar fertilizers were prepared, with modified starch as adhesive, and bentonite, humic acid as supplementary. The ratios of biochar in fertilizers were 10% (T1), 15% (T2), 20% (T3), 25% (T4) and 30% (T5) respectively. All the fertilizers were screened considering the microstructure, nutrient release rate, particle size and compressive strength and other basic properties. A pot experiment was carried out with the screened biochar fertilizers (CT2, CT3, CT4 and MT1, MT2 and MT3), taking common compound fertilizer (NPK) and no fertilizer as the control (CK). The differences of ammonia volatilization and nitrogen leaching and loss in paddy soil were analyzed. The results showed that the larger ratio of biochar resulted in the compacted fertilizer structure and the lower cumulative nitrogen release rate. However, the excessive addition of biochar would cause the uneven particle size and non-standard compressive strength of fertilizer. For CT, 15%~25% biochar was suitable. For MT, 10%~20% biochar was suitable. Compared with NPK, CT2, CT3 and CT4 reduced ammonia volatilization accumulation by 12.95%, 27.96% and 23.82%, and ammonia volatilization loss rate by 16.56%, 35.67% and 30.57%, respectively, among which CT3 had the best effect. The cumulative amount of ammonia volatilization was reduced by 33.72%, 41.48% and 16.06% respectively in MT1, MT2 and MT3, and the loss of ammonia volatilization was reduced by 43.31%, 53.18% and 20.38% respectively. The average concentration of ammonium and nitrogen in surface water decreased by 20.74% (CT4) and 39.90% (MT2), respectively, compared with NPK. Total nitrogen and nitrate nitrogen concentration of MT decreased by 5.50% and 5.09% respectively in MT2, while the difference of CT was not significant. Compared with NPK, CT significantly reduced the average concentration of ammonium nitrogen and total nitrogen by 8.93%~14.00% and 8.84%~16.38%, respectively, while there was no significant difference in nitrate nitrogen treatments. The average concentrations of ammonium nitrogen, nitrate nitrogen and total nitrogen were reduced by 11.16%~12.42%, 3.22%~22.29% and 11.14%~15.86%, respectively. The higher the ratio of biochar was, the more obvious the emission reduction of biochar was. But the effect was not obvious when the excessive biochar was added. In general, the two methods could effectively reduce the loss of ammonia volatilization and reduce the loss risk of nitrogen. Among them, the CT with 20%~25% biochar content was the best, and the MT with 15% was the best.