Design and Performance Evaluation of NPK Briquette Applicator for Small-Scale Upland Crops

Purpose Surface broadcasting application of prilled nitrogen, phosphorus, and potassium (NPK) fertilizer by hand in small-scale upland crops is time-consuming, labor-intensive, and wastes of a significant amount of fertilizer, contributing to greenhouse gas (GHG) emissions. Methods For this, a novel hand-held applicator for subsoil placement of NPK briquette was designed, developed, and tested both in the laboratory and experimental fields to evaluate applicator performance and its impact on field crop performance. The applicator works with the four mechanisms—feeding, metering, delivery, and subsurface placement with covering. The field experiment was conducted with four application treatments (NPK briquette application by applicator and hand, prilled NPK fertilizer as same dose and standard dose as applied by farmers). Results The result showed that the applicator had the highest consistent placement of NPK briquette (no losses) during laboratory and field tests. The applicator had a field capacity of 0.039 ha/h and field efficiency of 86.6%, which resulted in better performance than other application methods. The average hole coverage was 85.6%, the depth of placement was 77 mm, and the distance between the plant and the briquette application was 96.8 mm, all of which were close to the reference value. Moreover, crop yield was higher or similar to NPK briquette application by the applicator but significantly ( p ≤0.05) higher than other application methods. The weight of the applicator is 1.8 kg, so farmers can efficiently operate this user-friendly applicator. Conclusion NPK briquette applicator has shown excellent performance and significant potential for accurate, consistent, and deep precision placement of NPK briquette in the crop root zone for upland crops. Furthermore, the applicator has several advantages, including lower fertilizer costs and less drudgery associated with hand placement, which encourages farmers on a small-scale upland crop production.