Agroecological practices are emerging as efficient alternatives to address the challenge of sustainable agriculture.
The objective of this study was to examine whether plant residue amendments from stems and leaves (SL) of an
agroforestry shrub (Piliostigma reticulatum) enriched with nitrogen (N) sources improve nutrient cycling in
Soudano-Sahelian cropping systems. The experimental design was organized into four replicates with six
treatments consisting of two treatments of SL residue amendments (amended and non-amended) in combination
with three treatments including additional N sources (natural soils, urea, and cowpea as intercrop). The results
showed that the activity of termites (Nasutitermes torquatus) and ants (Messor galla and Pachycondyla rufipes) was
12–13 and 2–3 times higher in the SL amended soils than in non-amended soils, respectively. The activity of
earthworms (Millsonia inermis) was highest in the SL amended soils associated with the cowpea intercrop, and
was significantly lower in the urea enriched soils. SL amendments and N enrichments had no effect on soil basal
respiration. The substrate-induced respiration with N substrates (L-alanine and L-arginineL) was 25 and 52 %
higher in the SL amended soils than in the natural soils without any N inputs, indicating N limitation of microbial
activity. This corroborates the higher C/N ratio (14.3) observed in the SL amended soils compared to the natural
soils without any inputs (10.3). The N enrichment decreased the C/N ratio of the SL amended soils but was not
efficient to alleviate microbial catabolic limitations, likely by switching from N to C limitation. Overall, the SL
amendments with or without N enrichments triggered temporarily the soil macrofaunal activity, increased the
NH4-N availability compared to that of NO3-N, and improved crop performance.

Keywords: Agroecology Biogenic structures C/N ratio Nitrogen availability Organic carbon Soil respiration agroecology Biogenic structure C/N ratio Nitrogen availability organic carbon