将秸秆转化为高碳含量和稳定性的生物炭施入土壤无疑可提升碳库，但也会影响土壤性状和作物生长。为评估秸秆生物炭在北方潮土（pH 8.30）的应用潜力，设每季生物炭施用量为0（对照）、2.25（低量）、6.75（中量）和11.3 t hm^-2（高量）（四季后总施炭量分别为0、9、27、45.2 t hm^-2）4个处理，通过2年小麦-玉米轮作小区试验，观测了作物产量、籽粒品质、氮素吸收和土壤矿质氮、pH、容重、水分的变化。结果显示，中量生物炭处理下第四季玉米产量增加8.43%；中、高量生物炭处理下四季作物总产量提高4.54%~4.92%。生物炭对小麦和玉米籽粒蛋白质、小麦湿面筋含量及容重无负面影响。作物地上部分氮素吸收、土壤矿质氮含量和pH各处理间无明显变化。中、高量处理下四季作物后土壤容重降低2.99%~10.4%，含水量增加10.3%~20.2%，最大持水量提高14.5%~15.0%。表明中、高量秸秆生物炭每季还田对作物有小幅增产作用，且不影响籽粒品质。土壤容重、水分、持水量等物理性状的改善可能是作物增产的重要原因。

Annually about 0.6~0.7 billion tons of crop straw is produced in China, however nearly half failed reasonable use, causing a series of problems such as resource waste and environmental pollution. Biochar, a pyrolyzed biomass high in carbon concentration and stable C, can improve soil carbon pool rapidly when applied to soil. The application of crop-straw derived biochar does not only increase carbon sequestration, reduce emission of greenhouse gases and improve soil quality, but also serve as an effective way to realize diversified comprehensive utilization of straw resource. Nevertheless, owing to its unique physico-chemical properties, biochar, once applied as a soil conditioner, would certainly alter soil property and then influence crop growth. In order to assess the potential of biochar in application to farmland of cambosols (pH 8.30) in North China Plain, a two-year field experiment (4 croppings or two cycles of wheat and maize crop rotation beginning in fall of 2011), was conducted in the Fengqiu Agro-ecological Experiment Station, Chinese Academy of Sciences, Fengqiu, Henan Province. The experiment was designed to have four treatments in biochar application rate, i.e. Treatment BC0 (0 t hm^-2; as control or CK), Treatment BC2.25 (2.25 t hm^-2; low level), Treatment BC6.75 (6.75 t hm^-2; medium level) and Treatment BC11.3 (11.3 t hm^-2; high level). The total biochar application rate of the 4 croppings was 0, 9, 27 and 45.2 t hm^-2, respectively. Each treatment had three replicates and the plots of the treatments were laid out in randomized complete block design (RCBD), 16 m² each in area. For wheat N 240 kg hm^-2 (urea), P₂O₅150 kg hm^-2 (triple superphosphate) and K₂O 90 kg hm^-2 (potassium sulfate) was applied, while for maize N 200 kg hm² and the same rate of P and K as for wheat were. P and K fertilizers were applied all at once as basal dressing, while N fertilizer was applied in split dosing, i.e. 60% as basal and the remaining 40% as side dressing at the jointing stage. The fertilizers were broadcast into the wheat fields, and applied in pits in the maize. The crops were irrigated after fertilizer application, and their subsequent water demand was met by rainfall. Crop yield, grain quality, N uptake, mineral N (NO₃^--N and NH₄⁺-N) in soil, pH, soil bulk density, water content and water holding capacity were monitored for all the plots. Results show that for the first three crops (wheat-maize-wheat) no statistically significant difference (p>0.05) in yield was found between CK and the other three treatments. When it came to the fourth cropping, the crop of maize increased its yield by 8.43% in Treatment BC6.75. The yield of the four crops were also increased by 4.92% and 4.54% in Treatments BC6.75 and BC11.3, respectively. Biochar application had no negative effects on protein content in wheat and maize grains or bulk density of and wet gluten content in wheat grain, however Treatment BC11.3 was found to have increased bulk density of and protein content in wheat grain. Although no significant effect of biochar addition was observed on nitrogen uptake and accumulation by shoots of the crops and soil mineral nitrogen and soil pH, nitrogen uptake and accumulation of the grains of the 4 crops increased by 6.55%~7.98%, soil water content in the plough layer by 10.3%~20.2%, and soil water holding capacity by 14.5%~15.0%, yet, soil bulk density decreased by 2.99%~10.4% in Treatments BC6.75 and BC11.3. All the findings suggest that successive application of crop straw derived biochar does have some positive effects on crop yield and no negative influence on grain quality, and that biochar has no significant effects on mineral nitrogen content in the topsoil or N uptake and utilization by crops. The beneficial effects of biochar of improving soil physical properties, like in bulk density, soil water content, and water holding capacity may be the major cause to yield increase after the application of biochar in cambosols. It is necessary to do some further in-depth studies on effect of long-term biochar application on soil water and nutrient dynamic and some other physico-chemical properties of cambosols and nutrient translocation in plant in the hope that the study may provide some scientific data to support extrapolation of the application of crop straw derived biochar in upland of North China.

国家自然科学基金项目(41001147, 41271312)、中国科学院南京土壤研究所知识创新项目(Y11200000010)、土壤与农业可持续发展国家重点实验室优秀青年人才项目(Y412010006)资助