Introduction.

Weeds compete with coffee for water, light, and space; therefore, sustainable management practices must be implemented. Objective. To evaluate the effectiveness of weed management with ammonium nitrate and flaming in a coffee system. Materials and methods. This study was carried out from September 26, 2022, to January 10, 2023, at La Hilda coffee farm in San Pedro de Poás, Alajuela, Costa Rica. Two alternative weed control treatments were applied jointly: the first consisted of ammonium nitrate diluted in water at three doses (0, 150, and 300 kg/ha), followed 15 days later by flaming at three doses (0, 60, and 120 kg/ha). Applications targeted weeds present in the coffee rows, using a split-plot design where the main plot consisted of the ammonium nitrate doses and the small plots corresponded to flaming doses. A chemical control treatment with glyphosate, also combined with flaming, was included. Each treatment was randomly assigned and replicated six times. Results. Broad leaves were moderately damaged 25 days after nitrate application and 10 days after flaming. Both doses of ammonium nitrate without flaming caused slight damage to Commelina diffusa, and the highest ammonium nitrate dose without flaming produced moderate damage to broadleaf weeds; flaming without ammonium nitrate resulted in moderate initial damage to narrowleaf weeds. Conclusions. The herbicidal effect of ammonium nitrate was depended on flaming, but this effect was only observed in broadleaf weeds. C. diffusa was successfully controlled with glyphosate and flaming.