Design and Testing of a Low-Cost Wheel-Driven Crop Sprayer

Agriculture in Africa is an essential economic activity, employing about two-thirds of the continent’s working population. Much of the agricultural activities are confined to small-scale farming. The machinery available to most of these small-scale farmers requires significant manual labor, causing them to accumulate health problems and experience low production capacity. Small-scale farmers engaged in crop spraying rely on backpack sprayers, which leads to many of them citing back problems. High costs of alternatives, such as drone sprayers, prohibit their adoption. Here, the design, fabrication, and testing of a low-cost crop spraying device is presented. The device reduces the load-carrying effort required, as the user manually pushes a single-wheel frame carrying a tank and allows a gear-chain system to automatically operate the pump’s lever. The performance of the prototype is characterized by experimental testing, revealing that the device can carry a 50-liter tank while requiring a push effort equivalent to 32% of the load under firm mud conditions and staying below the design limit (50% of the load) for loose sand. Appropriate gear sizing was confirmed to enable an optimum flow rate of 1.2 L/min while the user walks with a regular gait, e.g., an operational speed of 1.45 m/s.