Compared with root nitrogen fertilizers, foliar nitrogen fertilizers (FNFs) have been widely used for crop growth due to their high fertilizer efficiency and high utilization rate, especially when the crops are deficient in nitrogen. Owing to the lotus leaf effect intrinsic to the leaf surface of crops, however, the majority of FNFs will easily slip from the leaf surface and be discharged into the soil environment by rainwater scouring, causing inferior utilization rates and serious soil pollution. Therefore, it is of paramount importance to remedy the adhesion capacity of FNFs on the leaf surface of crops for improving the utilization rate of FNFs. In this study, three kinds of micro–nanostructured silica spheres (e.g., solid silica spheres (S-Si), hollow silica spheres (H-Si) and sea urchin-like micro–nanostructured hollow silica spheres (SUH-Si)) with similar particle diameters (∼500 nm), different surface roughness, and diverse surface morphologies were utilized as carrier materials to load a nitrogen fertilizer to improve the utilization rate of FNFs on plant leaves. As a result, SUH-Si with the highest surface roughness among the three carriers leads to a change of adhesion capacity of the FNF on the surface of plant leaves, thus resulting in a superior infiltration effect of the nitrogen fertilizer. Compared with that of traditional FNFs, the adhesion capacity of the FNF with SUH-Si on peanut leaves and maize leaves was increased by 5.9 times and 2.2 times, respectively, resulting in a 2.29 times improved utilization rate of the FNF due to SUH-Si. Finally, contact angle measurements and microstructure analysis, as well as the calculation of interaction forces between the silica spheres and plant leaf surface, provided in-depth understanding to improve the adhesion capacity of foliar nitrogen fertilizers by surface roughness engineering of silica spheres. Our study would be helpful for developing FNFs with high efficiency and utilization rates by surface roughness engineering.

中文翻译：

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通过硅球表面粗糙度工程提高叶面氮肥的利用率

与根系氮肥相比，叶面氮肥（FNFs）因其肥料利用率高和利用率高而被广泛用于作物生长，尤其是当作物缺氮时。然而，由于农作物叶片表面固有的荷叶效应，大多数FNF容易从叶片表面滑落，并通过雨水冲刷而排放到土壤环境中，从而导致利用率低下和严重的土壤污染。因此，修复FNFs在农作物叶片表面的附着能力对提高FNFs的利用率至关重要。在这项研究中，三种微纳米结构的二氧化硅球（例如，粒径相似（〜500 nm），表面粗糙度不同的固态二氧化硅球（S-Si），空心二氧化硅球（H-Si）和海胆状的微纳米结构空心二氧化硅球（SUH-Si））多种表面形态被用作载体材料以装载氮肥，以提高植物叶片上FNF的利用率。结果，在三种载体中具有最高表面粗糙度的SUH-Si导致FNF在植物叶片表面上的粘附能力的改变，从而导致氮肥的优异渗透作用。与传统FNF相比，SUH-Si对FNF的粘附能力分别提高了5.9倍和2.2倍，导致SUH-Si使FNF的利用率提高了2.29倍。 。最后，接触角测量和微结构分析，以及二氧化硅球与植物叶片表面之间相互作用力的计算，为通过二氧化硅球表面粗糙度工程提高叶面氮肥的粘附能力提供了深入了解。我们的研究将有助于通过表面粗糙度工程开发具有高效率和利用率的FNF。