What agronomic and environmental factors drive coffee yield in Burundi? A country-wide study.

Abstract

Arabica coffee accounts for 70 % of Burundi's trade income. However, production has been steadily declining. The objective of this study was therefore to identify the agronomic and environmental factors driving coffee yield on smallholder farms across Burundi. For this purpose, a diagnostic survey was conducted on 155 coffee plantations across three key agroecological zones: Mumirwa, the Humid Central Plateau, and the Dry Central Plateau. Data collection included plot and management characteristics, soil fertility variables, and yield. Yield surveys were conducted over two successive years to account for production cyclicity. Principal component analysis, random forest and boundary line analysis were used for data analysis. Average yields of washed merchant coffee were 887 kg ha−1 for Mumirwa, 1115 kg ha−1 for the Humid Central Plateau, and 1268 kg ha−1 for the Dry Central Plateau, with maximum yields reaching 1891, 2533, and 2262 kg ha−1, respectively. Based on the random forest analysis, soil organic carbon, mulch thickness and soil magnesium content were the most important variables for explaining yield. On average, Burundi’s coffee plantations experience a 59 % yield deficit. The most yield-limiting factors included inadequate weeding and mulching, aging plantations, soil acidity, as well as phosphorus, exchangeable bases and soil organic carbon content. These factors varied across regions. Renewal of plantations, better management practices, and addressing specific soil fertility issues are key to improve yields, for which the study proposes revised norms. The study also highlighted the importance of considering coffee yield cyclicity to avoid misidentifying yield-limiting factors