生物炭与化肥配施对土壤主要物理特性的影响

摘要

以2013～2015年哈尔滨生物炭田间定位试验为研究对象,探索了普通化肥(NPK)、化肥+生物炭1(15.75t·hm-2,BC1)、化肥+生物炭2(31.50t·hm-2,BC2)、化肥+生物炭3(47.25t·hm-2,BC3)对东北黑土区大豆连作下土壤团聚体组成及稳定性指标、水力学性质及孔隙组成的影响.结果表明:(1)整体上看,生物炭施用显著增加了大团聚体含量,增大了团聚体稳定性指标-平均重量直径(MWD)值,同时土壤有效含水量、总孔隙度及有效孔隙均显著增加.(2)各处理优势水稳性团聚体均为0.25～0.50mm,BC1水稳性大团聚体数量增加16％,增幅最大,该处理平均重量直径值最高,为0.75mm;与单施化肥对照相比,生物炭显著降低了其他处理土壤萎蔫含水量(θr),提高土壤有效含水量,但炭量变化对土壤饱和含水量(θs)影响不显著;同时渗透系数平均升高4.3mm·min-1以及土壤饱和含水量平均提高0.12cm3·cm-3.与NPK相比,BC1处理渗透性最好(提升46％),饱和含水量在48％以上,总孔隙度最高(增加8.8％),团聚体结构表现最稳定,玉米秸秆生物炭在15t·hm-2时土壤物理属性最佳.(3)随着生物炭量继续增加,土壤细颗粒移动至已生成的有效孔隙中,BC2和BC3处理有效孔隙5～30μm,0.1～5μm和0.01～0.1μm不同程度减少,因而有效含水量也减少,总孔隙度降低至50％和51％;各处理团聚体稳定性指数与各粒级粘粒和碳酸钙含量的相关性均可选用一元二次方程表达,BC2和BC3处理由于施炭量增加土壤团聚体凝聚性降低,大团聚体数量减少,造成土壤结构稳定性相对降低.该结论为黑龙江典型黑土区利用农田有机废弃物进行培肥和结构修复提供科学参考,为生物炭在大豆农田系统推荐用量上提供理论借鉴.%Based on the biochar a pplication experiment (2013-2015), the rates of 0, 15.75, 31.50 and 47.25 t·hm-2 biochar combined with chemical fertilizer separately were applied under continuous soybean system in typical black soil region in Northeast China, the effects on soil aggregates, hydraulics and pore distribution were investigated. The results showed that: (1) the amounts of macro-aggregates and their stability indices (Mean Weight Diameter, MWD) were significantly increased with the biochar amendments, as well as the soil available water content, total porosity and available pore. (2) The sizes of dominant aggregates of the four treatments were all in the range of 0.25-0.50 mm by wet-sieving method. Compared with NPK treatment, the highest amount of macro-aggregates was increased by 16 ％ and the highest MWD value was 0.75 mm. Soil wilting point and soil available water content were significantly increased and decreased respectively due to biochar application for the additive treatments compared with CK but there was no significant changes for soil saturated water content. Meanwhile, penetration coefficient and soil saturated water content in average were both increased by 4.3 mm·min-1 and 0.12 cm3·cm-3 respectively due to biochar amendment. Compared with NPK treatment, the penetration capacity(increased by 46％) and total porosity(increased by 8.8％) were both the highest, the saturated water content was more than 48％ for BC1, the aggregation structure was the most stable and the physical characteristics of biochar-amended soil should be optimal at the rate of 15.75t·hm-2. (3) With excessive biochar application, biochar fine particles were moved and filled into effective pore, and these pore sizes of 5-30 μm,0.1-5 μm and 0.01-0.1 μm for BC2 and BC3 decreased, total porosities were reduced to 50％ and 51％. Quadratic equations were chosen to express the correlation between clay content/CaCO3 concentration and MWD values of all aggregate sizes. The amount of soil aggregates became less and its structure was less stable for excessive biochar-amended soil. The results provide the scientific references for fertilization and structure remediation and theory reference for biochar field application recommendation rates for soybean farmland.