不同生物炭施加量的土壤水分入渗及其分布特性

为了揭示生物炭施加到黑土区土壤后形成的特殊双层土壤结构对土壤水分入渗及其分布的影响,该研究采取室内与田间试验相结合的方法,探讨了积水入渗条件下不同生物炭施加量(0、10、20、40和80 t/hm~2)的土壤水分入渗特性,并建立了生物炭-土壤双层土壤结构水分分布模型,对不同生物炭施加量的农田土壤水分分布进行了模拟。结果显示,生物炭-土壤双层结构土壤水分入渗过程表现为斜率由大变小的两段非线性曲线,转折点为入渗锋面到达生物炭-土壤交界面后暂停继续下渗,上层土壤质量含水率累积到界面含水率超过临界含水率42.5%的时间;生物炭的施加使土壤入渗率、饱和导水率和临界吸力与对照相比提高的比例范围分别为21.95%~112.20%、14.29%~52.38%和13.75~78.69%,同时也可显著增强上、下层土壤的持水性能。在上层土壤厚度为20 cm时,影响临界吸力的因素只有生物炭的施加量,且其与施炭量的相关性大于土壤入渗率和饱和导水率;施用生物炭条件下的土壤水分分布规律可以用本研究所建立的生物炭-土壤双层土壤结构水分分布模型来表达。研究表明,生物炭添加能够改善黑土区土壤持水能力和水分入渗特性,有利于作物生长,减少地表径流和水土流失;同时也为生物炭在黑土区农业生产上的应用选择合理施加量提供科学参考。

Soil water infiltration and distribution characteristics under different biochar addition amount

Abstract: Biochar is derived from the pyrolysis of biomass, and when buried in soil, it can play the role of long-term soil carbon storage. Evidence suggests that biochar can improve soil fertility and crop production in some circumstances. Aimed to the special double-layer soil structure formed by putting the biochar into the farmland soil, the soil water infiltration characteristics of different addition amounts of biochar (0, 10, 20, 40 and 80 t/hm2) were studied under the condition of ponding infiltration. The study was conducted by the verifying experimental study and model simulation, and combined the laboratory experiment and the field experiment. In field experiment, the field plots were used with the different biochar application rates, the trial was fully randomized with 3 replications, and the biochar was mixed into the topsoil before the soybean was sown. The water distribution model of biochar-soil double-layer soil structure was established and the farmland soil moisture distribution of different addition amounts of biochar in the field was simulated. The results showed that the water infiltration process of biochar-soil double-layer soil structure was composed of 2 nonlinear curves and their slopes were getting smaller. When the wetting front reached the interface between biochar and soil, the infiltration would be temporarily stopped, and the downward water in soil was accumulated on the upper layer until the water content at the interface surpassed 42.5% of the critical water content, which was the time of the turning point of the 2 curves. The soil infiltration rate, the saturated hydraulic conductivity and the critical suction were improved by the addition of biochar, and they were increased by 21.95%-112.20%, 14.29%-52.38% and 13.75%-78.69% respectively when compared with the control group. And the biochar addition also improved the storage capacity and the water content of the upper and lower layers; under the treatment of 80 t/hm2 biochar addition, the water content of the upper layer increased by 35.08%, and the lower layer increased by 13.09%-19.96%. Therefore, the influence of the biochar addition on the upper layer was stronger than that of the lower layer. When the thickness of the upper soil was a constant value of 20 cm, the factor that affected critical suction was only the amount of biochar addition, and the correlation between them was greater than the other 2 infiltration parameters, i.e. the soil infiltration rate and the saturated hydraulic conductivity. Through the verification of the model predictions and field measurements of soil moisture, the distribution regulation of soil moisture can be expressed by the model established in the research under the condition of applying the biochar.