Our Research Reducing runoff and environmental impact of agricultural sprays

The spraying of chemicals in agriculture is very inefficient. Farmers use large quantities of chemicals, especially pesticides, to protect their plants and increase their yield but, eventually, only ~2% of these chemicals reach their intended target. The rest pollutes soils, surface water and groundwater in areas much larger than the fields themselves. A study found that pesticides could be detected 90% of the time in agricultural streams, 50% in shallow wells and 33% in major deep aquifers across the USA. These large losses also result in higher costs of chemicals for the farmer. One of the main reasons of this inefficiency is that many plants are hydrophobic, which means that they repel water. Therefore, impinging droplets from sprays, which are usually water-based solutions, can easily bounce or roll off plant surfaces and end up in the soil. The second big problem is wind drift: when small droplets are sprayed, they can easily be carried away by wind and end up out of the field. Current solutions are inefficient and are limited by a tradeoff between solving these two problems and end up having very low efficiencies.

To solve this problem, this research team developed novel spray formulations comprising charged molecules to improve agricultural pesticide application practices. These new formulations can cause the pesticide-laden drops to efficiently stick to leaf and fruit surfaces without rolling off, thereby preventing pollution of soils, surface water, and groundwater.

Charge interactions typically occur at faster timescales compared to hydrodynamic timescales. By spraying oppositely charged solutions simultaneously, the team introduced new electrostatic forces beyond the inertial-capillary forces that govern drop impact and could therefore arrest droplets readily on plant surfaces. In this project, they used this principle to conduct systematic studies on plants, optimize the charge interactions for adequate delivery and quantify the efficiency of these sprays at scales large enough to meet the needs of industrial farms.

Lab-scale results have demonstrated that their technology can reduce the amount of pesticide sprayed by a factor of ten. The project team developed this technology into additives for pesticide sprays for a range of plants and field conditions and conducting field studies. These enhanced spray solutions could have a game-changing impact on pesticide application practices, improving the efficiency and cost-effectiveness of pesticide applications, enhancing the flexibility of spray application, and significantly reducing run-off pollution.