The hazard for recurring food insecurity in the Sahel is largely affected by insufficient biomass productivity of degraded, marginal lands. In general, Water and Soil Conservation (WSC) techniques are believed to tackle the deterioration of soil quality by enhancing soil hydraulic properties, soil life and soil organic carbon content (SOC), but this beneficial effect on soil quality is hardly ever quantified in WSC research. This study therefore evaluates the effect of WSC on soil chemical, physical and biological quality indicators by means of an in situ experiment, which was installed in 2011 nearby Sadoré, Niger. The treatments include: zaï + manure (Z), demi-lunes + manure (DL), scarification + manure (SCAR), control + manure (CF) and control (C). WSC increases grain yields up to 0.7 ± 0.2 Mg ha−1 on degraded, marginal lands, which is similar to yields produced on fertile lands in the area. Nevertheless, a trade-off between biomass production and SOC accumulation was observed. After three growing seasons, SOC was found to rise significantly for the treatments provided with manure, from ± 2.5 to ±5 g kg−1, but the increase was lowest for Z, which produced highest yields. WSC also showed significantly elevated nematode counts, but did not considerably affect other soil chemical and soil physical properties. Hence, on the short term, WSC does not improve soil quality, as was widely proclaimed. Therefore, future research should include the assessment of long term WSC effects and the evaluation of integrated management combining WSC with alternative, yield-enhancing strategies.