Fostering plant growth and improving agricultural yields by adding “macro”-sized biochar to soil has been extensively explored. However, the impact and mechanism of action of aqueous extracts of biochar applied as foliar fertilizer on plant growth and physiology is poorly understood, and was the objective of this study. Extracts were produced from biochars derived from pine wood:clay:sand (PCS-BC; 70:15:15) and wheat straw:bird manure (WB-BC; 50:50) and tested at two dilutions each. The plant influence of the biochar extracts and dilutions were compared with chemical fertilizer made up to the same minor trace element compositions as the applied extracts and a control treatment consisting of only deionized water. The WB-BC extract was more alkaline than the PCS-BC extract and exhibited higher electrical conductivity values. Similar to the biochars from which they were derived, the WB-BC extract had higher concentrations of dissolved mineral elements and organic matter than the PCS-BC extract. Despite major differences in chemical composition between the PCS-BC and WB-BC extracts, there was virtually no difference in plant performance between them at any chosen dilution. Foliar application of PCS25, WB50, and WB100 led to a significant increase in the plant fresh biomass in comparison to their corresponding chemical fertilizer and to deionized water. Plant growth parameters including number of leaves and chlorophyll contents in plants treated with biochar extract foliar sprays were significantly higher than in all the other treatments. Electron microscopy and spectroscopy studies showed the deposition of macro- and nanoscale organomineral particles and agglomerates on leaf surfaces of the examined PCS25-treated plant. Detailed study suggests that carbon nanomaterials and TiO2 or Si-rich nanoscale organomineral complexes or aluminosilicate compounds from biochar extract were main contributors to increased plant growth and improved plant performance. These results suggest that biochar extracts have the potential to be used as nanofertilizer foliar sprays for enhancing plant growth and yield.

中文翻译：

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有机矿物活化生物炭提取物的施肥行为：低剂量叶面施用促进生菜生长

通过向土壤中添加“宏观”大小的生物炭来促进植物生长并提高农业产量。然而，作为叶面肥的生物炭水提取物对植物生长和生理的影响及其作用机理了解甚少，这是本研究的目的。从松木：粘土：沙子（PCS-BC； 70：15：15）和麦草：鸟粪（WB-BC； 50：50）衍生的生物炭中提取提取物，并分别进行两种稀释测试。将生物炭提取物和稀释液对植物的影响与化学肥料进行了比较，该化学肥料的微量元素组成与所施用的提取物相同，仅由去离子水组成。WB-BC提取物比PCS-BC提取物更具碱性，并且具有更高的电导率值。与从中提取生物炭类似，WB-BC提取物比PCS-BC提取物具有更高的溶解矿物质和有机物浓度。尽管PCS-BC和WB-BC提取物之间的化学成分存在重大差异，但在任何选定的稀释度下，它们在植物性能上几乎没有差异。与相应的化肥和去离子水相比，叶面施用PCS25，WB50和WB100导致植物新鲜生物量显着增加。用生物炭提取物叶面喷雾剂处理的植物的植物生长参数（包括叶片数和叶绿素含量）显着高于所有其他处理方法。电子显微镜和光谱学研究表明，宏观和纳米级有机矿物质颗粒和附聚物在经PCS25处理的植物叶片表面上的沉积。详细的研究表明，碳纳米材料和生物炭提取物中的TiO2或富含Si的纳米级有机矿物复合物或铝硅酸盐化合物是促进植物生长和改善植物性能的主要因素。这些结果表明，生物炭提取物具有用作提高植物生长和产量的纳米肥料叶面喷雾剂的潜力。