Enhancing productivity and quality of shade-grown Robusta coffee ( Coffea canephora ) through foliar application of amino acid-based bio-stimulant

Premature fruit drop and inefficient nutrient utilization are major constraints affecting productivity and quality in Robusta coffee. Amino acid-based bio-stimulants have shown potential in enhancing nutrient assimilation and stress tolerance; however, their effectiveness under field conditions in coffee requires systematic evaluation. This study aimed to assess the impact of foliar application of amino acid-based bio-stimulants on yield, quality, and economic returns of Robusta coffee, with particular emphasis on reducing premature fruit drop. A field experiment was conducted using a randomized complete block design with nine treatments and three replications. Among the treatments, foliar application of bio-stimulant at 0.16% in combination with a nutrient mixture resulted in significantly higher growth and yield attributes, including increased bearing nodes (19.12 ± 0.20), fruit retention (76.08 ± 1.38), and clean coffee yield (1217 ± 0.87 kg clean coffee ha−1), compared to the planter’s practice (15.54 ± 0.28, 69.48 ± 0.47, and 999 ± 1.35 kg ha−1) (p ≤ 0.05). Quality parameters, including the proportion of ‘A’ grade beans (48.99 ± 0.58) and cup quality score (68.5 ± 0.63), were also significantly improved under T7. Economic analysis indicated higher net returns (₹ 42962 ± 514) and benefit–cost ratio (1.50 ± 0.03) for T7 relative to the control treatment (₹19,354 ± 282 and 1.22 ± 0.05). The improved performance was attributed to enhanced nutrient uptake, better hormonal balance, and reduced fruit drop. In conclusion, foliar application of amino acid-based bio-stimulants, particularly in combination with a balanced nutrient mixture, can be an effective strategy to improve productivity, quality, and profitability of Robusta coffee under field conditions.