Improving utilization rate of foliar nitrogen fertilizer by surface roughness engineering of silica sphere

Compared with root nitrogen fertilization, foliar nitrogen fertilizer (FNF) has been widely used for crops growth due to its fast fertilizer efficiency and high utilization rate, especially when the crops are deficient in nitrogen. Owing to the lotus leaf effect inherent on the leaf surface of crops, however, the majority of FNF will be easily slipped from leaf surface and discharged into the soil environment by rainwater scouring, causing inferior utilization rate and serious soil pollution. Therefore, it is of paramount importance to remedy the adhesion capacity of FNF on leaf surface of crops for improving utilization rate of FNF. 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-nanostructure 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 nitrogen fertilizer for improving utilization rate of the FNF on plant leaves. As a result, the SUH-Si with the largest roughness surface among of three carriers leads to the change of adhesion capacity of FNF on the surface of plant leaf, thus resulting in superior infiltration effect of nitrogen fertilizer. Compared with the traditional FNF, the adhesion capacity of FNF with SUH-Si on peanut leaf and maize leaf were increased by 5.9 times and 2.2 times respectively, resulting in 2.29 times improved utilization rate of FNF by SUH-Si. Finally, the contact angle measurement, microstructure analysis, as well as the calculation of interaction forces between silica sphere and plan leaf surface provided in-depth understanding for improving adhesion capacity of foliar nitrogen fertilizer by surface roughness engineering of silica sphere. Our study would be helpful for developing high-efficiency utilization rate of FNF by surface roughness engineering.