Impact of Integrating Annual and Perennial Legumes under Coffea arabica on Sloping Land

Above-ground biomass cover under Coffea arabica on sloping land is beneficial but difficult to sustain. Interplanting annual and perennial legumes can sustain the above-ground biomass cover, and improve soil fertility, yield, and profitability. This was tested on 26 sloping farms in a four-growing season experiment on undersowing C. arabica with new crop combinations: Mucuna pruriens var. utilis (T1); Millettia dura Dunn (T2); a combination of M. pruriens and M. dura (T3); and the control with a no-cover legume (T4). On each farm, all treatments followed a randomized single-block design. T3 produced 8.7 mt/ha/yr above-ground biomass that was significantly (p < 0.01) higher than other treatments and was increasing with the seasons. Under T3, plant-available nitrogen (N) and potassium (K) increased more than in other treatments. During the fourth season, coffee yield in T3 was 54%, 22%, and 11% higher than in T4, T2, and T1, respectively. The gross profit under T3 was 86% higher than in T4 in the fourth season. This indicates that interplanting a combination of M. pruriens and M. dura under C. arabica on sloping land can sustainably increase above-ground biomass cover, soil's plant-available N and K, coffee yield, and profitability. Based on the results, the combination of M. pruriens and M. dura is recommended to optimize coffee production under the described conditions.