Fallow is one of the methods used to restore soils fertility and to produce fodder for domestic animals. The objective of this study was to compare the biomass yields of different species of shrubs and grasses in contrasting soils in South Kivu Province in the Eastern of Democratic Republic of Congo. The experimental design was a randomized block containing four repetitions. Each repetition contained four plots corresponding to four species of gramineas (Pennisetum purpureum, Setaria sphacelata, Brachiaria ruziziensis and Tripsacum laxnum) or shrubs (Albizzia chinensis, Leucaena diversifolia, Calliandra calothyrsus and Leucaena leucocephala). Highly significant differences (P = 0.001) were observed between species and between sites for all observed parameters. The quantities of biomass produced by the Pennisetum in the two sites (29.31 t/ha) were significantly higher than those produced by the 3 others species followed by Setaria (19.54 t/ha), Brachiaria (13.84 t/ha) and Tripsacum (13.8 t/ha). The same trend was observed for shrubs species, the quantities of biomass produced by the Calliandra in the two sites (11 t/ha) were significantly higher (P = 0.001) than those produced by the 3 others species followed by Leucaena diversifolia (8 t/ha), Leucaena leucocephala (3 t/ha) and Albizia chinensis (2 t/ha). Concerning the sites, a highest significant difference was observed between the two sites, the biomass yields produced at Mulungu (7.3 and 23.7 t/ha) were significantly higher than those for Mushinga (4.7 and 14.5 t/ha), for shrubs and gramineas respectively. For forage biomass production and soil productivity restoration, the combination of Calliandra and Leucaena diversifolia, and pennisetum-setaria can be used as improved fallow in the conditions of the trial sites. There is a need for follow-up research on soil production restoration to include these four species in trial at both sites in South Kivu Province.

Better managements of soil fertility are imperative for rehabilitating degraded soil in order to increase crop yields. Our objective was to assess the effect of improved fallow of different combinations of herbaceous-shrubs species and microdose of fertilizer on maize-bean yield, aboveground organic carbon sequestration and soil proprieties improvement. The treatments consisted of Pennisetum purpureum, Setaria sphacelata and Tripsacum laxum or Tithonia diversifolia combinations with 3 shrub species (Leucaena diversifolia, Calliandra calothyrsus, and Albizzia chinens) and microdoses of fertilizer (NPK-manure), two controls treatments without fertilizer were also included. These treatments were arranged in a split-plot design with, the main plot treatment consisting of herbaceous-shrubs fallow type subdivided into four subplots of beans ([M211], [NAMULENGA] [CURANTINO] and [VCB] cropped with three maize varieties [SamVita A and B], and [Gv664]. Application of microdose and herbaceous species combination increased bean and maize grain yield at both sites 21 months after trial initiation. No significant difference was observed between the different combinations in both sites and for the 3 planting seasons for assessed parameters. Herbaceous combinations increased significantly the number of nodules (P < 0.01). Highest biomass yield, C sequestration number and biomass of earthworm were found in the herbaceous-shrubs combinations treatments and lower in NPK-manure and control treatments in both sites. In addition, the number of earthworms was enhanced with application of microdose of fertilizers (546) and herbaceous-fallow grassland (725) compared to control (282) 2 years after trial initiation at Mulungu site. No significant difference was observed between the different combinations in both sites for soil temperature and moisture variation.