Improving the surface contact area of NPK fertilizer droplets on leaf surface models of varying hydrophobicity

Abstract

The coffee ring phenomenon referred to the ring-like stain left behind by a sessile droplet as it evaporated. The phenomenon has limited the improvement of various processes, from inkjet printing and microdot array to coating. In agriculture, the coffee ring effect inhibited the adsorption of foliar fertilizers droplets applied onto leave surfaces to induce plant growth, causing fertilizer run off which consequentially damaged the ground water and marine life. In this study, the possibility of adding SDS and dextrin to NPK solution to mitigate the coffee ring effect was explored. Fertilizer samples were tested on modified glass substrate to mimic the hydrophobic characteristic of leaves in nature. The fertilizer coverage of various fertilizer samples was taken; the results showed an improvement in the coverage of NPK droplets with both SDS or dextrin as compared to standard NPK droplets, indicating the necessity of having both components in the system. To investigate the concentration of SDS and dextrin that best improve the coverage, response surface methodology was applied. However, no specific SDS and dextrin concentration was obtained but rather, high coverage values were recorded within the range of 3.0 – 4.0 mM SDS and 2.6 – 3.0 mM dextrin was applied.