Biochar Engineering & Technology Research Center of Liaoning Province, Rice Research Institute, Agronomy College, Shenyang Agricultural University, Shenyang 110866, Liaoning, China.
Biochar Engineering & Technology Research Center of Liaoning Province, Rice Research Institute, Agronomy College, Shenyang Agricultural University, Shenyang 110866, Liaoning, China.
Sci Total Environ. 2021 Jun 15;773:144564. doi: 10.1016/j.scitotenv.2020.144564. Epub 2021 Feb 2.
Albic soil is a low-yielding soil that is widely distributed in Northeast China. The high viscosity and acidity and the lack of nutrients in the Albic layer limit the growth of crop. In our previous studies, we found that applying biochar as a soil amendment could improve the properties of Albic soil and promote soybean growth. Increases in the nitrogen contents of the soil and the soybeans were key aspects of these improvements. Soybean is a nitrogen-fixing crop, the increase in nitrogen in the Albic soil may have been due to an improvement in biological nitrogen fixation by the soybean with biochar amendment, but the function mechanism was still uncertain. We hypothesized that biochar could improve biological nitrogen fixation of soybean by affecting soybean root growth in the Albic soil. Therefore, we conducted pot experiments with five treatment levels (0, 10, 20, 30, and 40 g·kg biochar) for two years to study how biochar affects the root growth strategy and biological nitrogen fixation of soybean based on its root structure and root nutrient acquisition ability at different stages. The soybean root structure and activity indexes, nodulation ability and nitrogen uptake were measured at different growth stages; in the second year, at the late seed-filling stage, the stable N isotope method was used to elucidate the biological nitrogen fixation process. Regarding root structure at the pod-setting stage, biochar resulted in increases in root length density, specific root length, root diameter and specific tip density but a decrease in root tissue mass density at the pod-setting stage. Biochar improved root nutrient acquisition by increasing root activity, root tip number and root-bleeding sap amount. The change in root growth strategy contributed to the promotion of biological nitrogen fixation by the rhizobia that live symbiotically with soybean, thereby increasing crop yield.
白浆土是一种低产土壤，广泛分布于中国东北地区。白浆层的高粘度、酸性和养分缺乏限制了作物的生长。在我们之前的研究中，我们发现施用生物炭作为土壤改良剂可以改善白浆土的性质并促进大豆生长。土壤和大豆中氮含量的增加是这些改良的关键方面。大豆是一种固氮作物，白浆土中氮的增加可能是由于生物炭改良后大豆的生物固氮作用得到了改善，但作用机制仍不确定。我们假设生物炭可以通过影响大豆在白浆土中的根生长来改善大豆的生物固氮作用。因此，我们进行了为期两年的五个处理水平（0、10、20、30 和 40 g·kg 生物炭）的盆栽试验，以研究生物炭如何通过不同阶段的根结构和根养分获取能力来影响大豆的根生长策略和生物固氮作用。在不同的生长阶段测量大豆根结构和活性指标、结瘤能力和氮吸收；第二年，在种子灌浆后期，采用稳定氮同位素法阐明生物固氮过程。关于结荚期的根结构，生物炭导致根长密度、比根长、根直径和比根尖密度增加，但根组织质量密度降低。生物炭通过增加根活性、根尖数量和根溢泌液量来改善根养分获取。根生长策略的变化有助于与大豆共生的根瘤菌的生物固氮作用的促进，从而提高作物产量。
