Use of leguminous cover crops (Mucuna pruriens and Desmodium intortum) to mobilize phosphorus from an Andosol in the volcanic highlands of North Kivu (Eastern DR Congo)

Low availability of phosphorus (P) bound by amorphous minerals, losses of soluble P due to soil erosion and phosphorus exports in crops are among the main constraints to agricultural production in the volcanic highlands of North Kivuin the Democratic Republic of Congo. This study was carried out to determine the capacity of cover legumes (Mucuna pruriens and Demodium intortum) to influence soil P mobilization for the improvement of phosphate nutrition in maize cultivated on young andosol. To this end, an experiment was conducted using a randomized and subdivided complete block design (Split-plot) comprising five cropping systems (monoculture maize; maize+Mucuna as a catch crop; maize+Mucuna in PCCS; maize+Desmodium as a catch crop; maize+Desmodium in PCCS). Treatments were repeated 4 times over two cropping seasons (September 2023 and February 2024). The results showed that the soil was a Vitric Lomic Sideralic Andosol, corresponding to a young Andosol on basic pyroclastic material with a low available P content (1.6% of total P), giving a retention rate of 98.5%.The maize+Mucuna PCCS combination produced the most significant improvement in soil-available P and phosphate nutrition in maize. By incorporating 19.7t/ha of dry biomass of Mucuna pruriens into the soil, available P increased from 1.6% to 3.9%, i.e. an increase of 28 mgKg^-1 of P compared with the pre-crop concentration. Improved P nutrition also led to an increase in maize grain yields of 4 t/ha and dry biomass yields of 13 t/ha from September 2023 to February 2024. In addition, P exports in harvested maize grain increased from 3.7Kg/ha in the September 2023 season to   19.8Kg/ha in the February season, with no significant reduction in soil P mobilization. Thus, the Maize+Mucuna association in PCCS is recommendable for optimizing phosphate nutrition in the andosols of the volcanic highlands of North Kivu.