Biochar (BC) has gained worldwide attention as a soil amendment to improve soil fertility and crop yield. However, long-term field data are still lacking to evaluate the effectiveness of BC application in increasing crop yield under various specific site conditions. A 7-year field experiment of BC application with consecutive corn-wheat rotations was carried out in a semi-humid region in the HuangHuaiHai Plain in north China. Straw-derived BC was mixed with the sandy loam soil in 9 m2 (3 m × 3 m) plots to a depth of 20 cm with the application rates (w/w) of 0 t ha−1, 12 t ha−1, 24 t ha−1, 36 t ha−1, 48 t ha −1, and 60 t ha −1, respectively. Physiological indexes, e.g. plant height, spike number, number of ears, spike length, straw dry matter and root dry matter, and the crop yield, i.e. 1000-grain weight, and grain yield, were measured for each growing season under different BC treatments. Disturbed and undisturbed soil samples were collected 4 years after BC application. Laboratory measurements were conducted to determine soil properties, such as bulk density, saturated hydraulic conductivity (Ks), aggregate size distribution, soil water retention characteristics, pore size distribution, and soil nutrient contents under different BC treatments. The results showed that plant physiological indexes and grain yield of both corn and wheat were not significantly affected by BC application, being independent of the application rate, climate variation and time. Besides, the BC application significantly improved soil physio-chemical properties, indicated by increases in soil macro-aggregate, aggregate stability, Ks, plant available water capacity and soil available nutrients. The long-term field results demonstrate that the soil fertility improved by BC application may not always lead to significant increase in crop yield. Apart from soil properties, genetic merits of the specific crop cultivar and field managements of irrigation and fertilization could be the dominating factors affecting crop growth and yield under particular soil type and climate conditions. Thus, applying BC as a soil amendment to improve crop yield should be approached with comprehensive consideration of the local environmental conditions, crop cultivars and field managements.

中文翻译：

---

生物炭施用对黄淮海平原半湿润地区作物生长和产量不改善：连续 7 年的田间试验


生物炭 （BC） 作为一种提高土壤肥力和作物产量的土壤改良剂而受到全世界的关注。然而，仍然缺乏长期的田间数据来评估 BC 应用在各种特定场地条件下提高作物产量的有效性。在华北黄淮海平原的半湿润地区进行了为期 7 年的玉米-小麦连续轮作 BC 施用田间试验。将秸秆衍生的 BC 与 9 m2（3 m × 3 m）样地中的沙壤土混合至 20 cm 深，施用量 （w/w） 分别为 0 t ha-1、12 t ha-1、24 t ha-1、36 t ha-1、48 t ha -1 和 60 t ha -1。测定不同 BC 处理下每个生长季的株高、穗数、穗数、穗长、秸秆干物质和根干物质等生理指标，以及作物产量（千粒重）和产量。在 BC 施用 4 年后收集受干扰和未受干扰的土壤样品。进行室内测量以确定不同 BC 处理下的土壤性质，例如堆积密度、饱和导水率 （Ks）、骨料尺寸分布、土壤保水特性、孔径分布和土壤养分含量。结果表明，玉米和小麦的植株生理指标和产量均不受BC施用量、气候变化和时间的影响，与施用量、气候变化和时间无关。此外，BC 施用显著改善了土壤理化性质，表现为土壤大团聚体、团聚体稳定性、Ks、植物速效水容量和土壤速效养分的增加。 长期的田间结果表明，通过 BC 施用改善的土壤肥力可能并不总是导致作物产量的显着增加。除了土壤特性外，特定作物品种的遗传价值以及灌溉和施肥的田间管理可能是在特定土壤类型和气候条件下影响作物生长和产量的主导因素。因此，将 BC 作为土壤改良剂施用以提高作物产量时，应综合考虑当地的环境条件、作物品种和田间管理。