Biochar can improve a number of soil physical properties but few studies focused on the impacts of different biochars on soil Atterberg limits and mechanical strength in paddy fields. A field experiment was performed to evaluate the influences of five different biochars on soil physical properties of a paddy soil (Stagnic Anthosol). Biochars produced from rice straw (RB), maize straw (MB), wheat straw (WB), rice husk (HB) and bamboo (BB) were applied to the paddy field with the rate of 0, 11.25, and 22.5 t ha⁻¹, respectively. After three consecutive crops (rice-rape-maize) plantation, the biochar-amended soils were collected to determine a number of soil physical parameters. Compared with control treatment, the application of five biochars at the rate of 22.5 t ha⁻¹ significantly (p < 0.05) increased the content of macroaggregates larger than 5 mm in diameter and aggregate stability evaluated by Le Bissonnais’s methodology. Biochar treatments significantly (p < 0.05) increased soil water retention capacity at matric potential of -0.033 and -1.5 MPa, and consequently, enhanced available water content (AWC) in soil. Biochars at the rate of 22.5 t ha^-1 treatments increased the AWC by 15.5, 17.1, 26.4, 42.4, and 15.2 % for RB, MB, WB, HB, and BB, respectively. Biochar application could significantly increase the plastic index (PI) of soil, thus effectively extend soil cultivable water range. The application of biochar significantly reduced the tensile strength and cohesion, but no significant effect on internal frication angle of soil was observed. The application of biochars at the rate of 22.5 t ha⁻¹, on average, increased the yield of first season crop (rice) by 6.3∼13.3 %, but only RB and HB treatments significantly increased the yield of second season crop (rape), and RB, WB, and HB significantly increased the yield of third season crop (maize). The scanning electron microscope (SEM) image and elemental mapping of biochars indicated that biochar could alter pore characteristics (size distribution, shape, connectivity, and porosity) of soil, consequently affecting water retention and mechanical strength of soil. Overall, the HB exhibited the largest effect on the AWC, Atterberg limits, and crop yield. The biochar amendment increased the crop yield by improving soil workability for tillage operations and reducing mechanical resistance to crop root growth.

生物炭可以改善许多土壤的物理特性，但是很少有研究关注不同生物炭对水田土壤Atterberg限值和机械强度的影响。进行了田间试验，以评估五种不同生物炭对稻田土壤的物理特性的影响（Stagnic Anthosol）。将稻草（RB），玉米秸秆（MB），小麦秸秆（WB），稻壳（HB）和竹子（BB）产生的生物炭以0、11.25和22.5 t ha的比例施于稻田^{- 1}。在连续三季（水稻-油菜-玉米）种植后，收集经过生物炭改良的土壤，以确定许多土壤物理参数。与对照相比，以22.5 t ha ^-1的比例施用了5种生物炭（p <0.05）通过Le Bissonnais的方法评估了直径大于5 mm的大骨料的含量和骨料稳定性。生物炭处理显着（p <0.05）在基质势为-0.033和-1.5 MPa时增加了土壤保水能力，因此，增加了土壤中的有效水分含量（AWC）。生物炭的比率为22.5 t ha ^-1RB，MB，WB，HB和BB处理的AWC分别增加了15.5％，17.1、26.4、42.4和15.2％。生物炭的施用可以显着增加土壤的塑性指数（PI），从而有效地扩展了土壤可栽培水的范围。生物炭的施用显着降低了抗张强度和内聚力，但未观察到对土壤内部摩擦角的显着影响。生物炭的施用量为22.5 t ha ^-1，平均而言，第一季作物（大米）的产量提高了6.3％至13.3％，但是只有RB和HB处理显着提高了第二季作物（油菜）的产量，而RB，WB和HB则显着提高了第二季作物（油菜）的产量。第三季作物（玉米）。扫描电子显微镜（SEM）图像和生物炭的元素图谱表明，生物炭可能会改变土壤的孔隙特征（尺寸分布，形状，连通性和孔隙度），从而影响土壤的保水性和机械强度。总体而言，HB对AWC，Atterberg限值和农作物产量表现出最大的影响。生物炭改良剂通过改善耕作作业的土壤可加工性并降低对作物根系生长的机械抵抗力而提高了作物产量。