Circular bioeconomy valorization of coffee bark residues: Soil chemical transformation and yield enhancement in highland arabica coffee systems

Abstract

Comparative research on the effect of coffee bark composting on the yield of Arabica coffee in Phu Oi Village, Pak Chan District, Champasak Province was conducted. The objectives of the study were as follows: 1) to evaluate the quality of coffee bark compost and 2) the impact of the application of this compost on coffee yield. The research was conducted on a farmer's coffee farm in Phu Oi Village, Paksong District, with the comparative model on a 1-hectare plantation of Arabica coffee. The trees were planted with a spacing of 1.5 m x 1 m, totaling 6,600 trees. The coffee grounds compost was analyzed and determined to have 1.42% total nitrogen (% Total N), 6.32 ppm of useful phosphorus, 0.04 ppm of useful potassium, 28.35% organic matter and pH= 7.27. When comparing with the standards of the organic fertilizer of the Ministry of Agriculture and Forestry of Lao PDR (2000), the nitrogen, organic matter, and pH values were close to the standards. Compost changed the chemical characteristics of the soil, including P, N, and organic matter content, etc. Nitrogen content increased from 0.17% to 0.95% and phosphorus from 15.45 ppm to 19.50 ppm of soil. Organic matter content was increased from 3.33% to 15.75%. The pH of the soil was changed from 4.67 to 6.25 by the compost. The employment of coffee bark compost resulted in an increase in the Arabica coffee yield as compared to unfertilized farms. In 2022, the yield was 12 T/ha, this yield increased to 15 T/ha in 2023 with the application of compost, whereas in unfertilized farms, the yield was 11.5 T/ha. Thus, the use of compost in coffee cultivation contributes to the enhancement of nutrients and soil fertility, and consequently to improvement in coffee production, with the content of nutrients being equivalent to organic fertilizers.