Development of a manually operated organic and inorganic fertiliser applicator for smallholder farmers

This paper reports the design, fabrication and testing of a low-cost PVC-based manual fertiliser applicator (MFA) for the placement of granular and powdery fertilisers (organic and inorganic) at a required soil depth and plant spacing. The MFA consists of a spring-loaded trigger mechanism, a connecting tube and a knapsack plastic tank for the fertiliser storage, holding between 8.0–12.0 kg of fertiliser depending on the fertiliser's characteristics. The MFA was tested using four common fertilisers (NPK, SSP, Urea and organic manure) at different fertiliser moisture contents (3, 4, 5 and 6% w.b.). The results reveals that the MFA performed effectively in the fertiliser's discharges although it was significantly affected by the moisture content and fertiliser type. However, the MFA performed optimally when the moisture content was not above 4% (w.b.) giving optimal discharge values of 3.82, 3.45, 1.88 and 1.70 g per application for the NPK, SSP, urea, and pulverised organic fertilisers, respectively, at 4–7 cm application depths. Operators can, however, effectively determine the depth of placement and the number of applications during use based on agronomic recommendations.