Effects of drought stress at flowering stage on growth, flowering and fruit quality of coffee arabica

Spring drought in Yunnan frequently coincides with the flowering stage of coffee, yet its combined impact on floral development and bean quality remains unclear. Using two-year-old coffea plants, we imposed four irrigation regimes during anthesis: light drought (LD, 55–60% of field capacity), moderate drought (MD, 40%–45%), severe drought (SD, 25%–30%), and a well-watered control (CK, 75%–80%). Compared with CK, LD caused no significant changes in the numbers of flowers and fruits or in yield per plant. In contrast, MD and SD markedly inhibited growth: SD reduced floral bud and open-flower counts by 50% and 44%, respectively. Both MD and SD decreased fresh-fruit and green-bean transverse and longitudinal diameters, hundred-seed weight, fresh-to-dry weight ratio, and overall yield, and they altered the chemical composition of green beans. Collectively, the data indicate that maintaining soil moisture at ≥55% of field capacity during flowering avoids yield and quality losses. We therefore recommend this threshold as a practical irrigation standard for coffee cultivation in regions subject to spring drought.