Improving the utilization rate of foliar nitrogen fertilizers by surface roughness engineering of silica spheres

Abstract

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.