Biochar effects on soil properties, water movement and irrigation water use efficiency of cultivated land in Qinghai-Tibet Plateau

Biochar, has recently, been widely used as a potential soil additive to improve the quality of cultivated land. However, the effect of biochar on irrigation water use efficiency (IWUE) remains unclear in the Qinghai-Tibet Plateau (QTP). Therefore, the purpose of this study was to explore the effects of biochar on the soil properties, water infiltration, and irrigation water efficiency of QTP cultivated land. A column experiment with four biochar application levels (0, 3, 6, and 9 kg·m−2 denoted CK, BC1, BC2, and BC3, respectively) was conducted to explore the biochar effect on the soil water infiltration process. The soil bulk density (γ), saturated water content (θs), soil water retention curve (SWRC), specific water capacity C(h), and saturated hydraulic conductivity (Ks) were measured after the trial. The effects of biochar application level, biochar application depth, irrigation water depth, and initial soil moisture on water loss and IWUE were then simulated by HYDRUS-2D. The results showed that biochar slowed the process of soil water infiltration by changing the soil physical properties and hydraulic properties, reducing the water loss by 5%–15.02%, effectively alleviating the waste of irrigation water, and therefore increasing IWUE by 2%–9.43%. Water loss and IWUE were significantly associated with the biochar application depth and level. Additionally, a biochar level of 6 kg·m−2 showed the best effect for ameliorating the QTP's cultivated soil. These results provide a novel approach for reducing water loss and enhancing the irrigation water use efficiency of QTP cultivated soil. [Display omitted] •Biochar effects on soil in QTP were explored coupled with column experiments and model simulations.•Biochar improved soil water retention and decreased hydraulic conductivity.•Biochar reduced the leakage and alleviated the serious water loss risk.•The IWUE was significantly increased by 2%–9.43% by biochar amendment.•The biochar application level of 6 kg·m−2 had the most notable effects.