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Abstract. The impact of direct-seeding mulch-based cropping systems (DMC), direct seeding (DS) and tillage seeding (TS) on Sorghum yields, soil fertility and the rehabilitation of degraded soils was evaluated in northern Cameroon. Field work consisted of visual examination, soil sampling, yield and rainfall data collection. Three fertilization rates (F1: 100 kg ha −1 NPK + 25 kg ha −1 of urea in DMC, F2: 200 kg ha −1 NPK + 50 kg ha −1 of urea in DMC and F3: 300 kg ha −1 NPK + 100 kg ha −1 of urea in DMC) were applied to each cropping system (DS, TS and DMC), resulting in nine experimental plots. Two types of chemical fertilizer were used (NPK 22.10.15 and urea) and applied each year from 2002 to 2012. Average Sorghum yields were 1239, 863 and 960 kg ha −1 in DMC, DS and TS, respectively, at F1, 1658, 1139 and 1192 kg ha −1 in DMC, DS and TS, respectively, at F2, and 2270, 2138 and 1780 kg ha −1 in DMC, DS and TS, respectively, at F3. pH values were 5.2-5.7 under DMC, 4.9-5.3 under DS and TS and 5.6 in the control sample. High values of cation exchange capacity were recorded in the control sample, TS system and F1 of DMC. Base saturation rates, total nitrogen and organic matter contents were higher in the control sample and DMC than in the other systems. All studied soils were permanently not suitable for Sorghum due to the high percentage of nodules. F1 and F2 of the DS were currently not suitable, while F1 and F3 of DMC, F3 of DS and F1, F2 and F3 of TS were marginally suitable for Sorghum due to low pH values.

Local initiatives of hardé soils rehabilitation in Maroua region have been analyzed. Fieldwork consisted of conducting observations and surveys beside farmers in two study sites, Mizileng and Zokok. Investigations on perception of land degradation signs by farmers show that appearance of encrusted surfaces and loss of vegetation cover are signs more expressed in both study sites. Causes expressed include acceleration of water and wind erosion processes, excessive falling of trees, inappropriate farming techniques and climatic hazards. The main consequences are declining of crop yields, lack of farming land and loss of natural pastures. Rehabilitation actions undertaken by local communities surveyed include earth dikes, tillage including cart or hoe ploughing, application of organic matter, integrating farming techniques such as fallowing, association and rotation of crop, and lastly, parking of animals on plots to be rehabilitated. Populations assert that their majority perceive signs of real change on planning plots in six months to three years. Constraints to those rehabilitation actions include material requirements that are mostly not available or accessible to farmers in the study area and access to land. Globally, there is no integration of local knowledge in the implementation of projects and consequences are localized and ephemeral efficiency, neither conclusive results. Implementation of an innovation in rural areas must take into account the factors of ownership and inscribe a well-defined trajectory. This trajectory must be dynamic and reflexive where local knowledge will cope with expert knowledge to ensure impact and sustainability of innovation.

Spatial distribution of the seasonal changes (in %) between future and historical periods (2021–2050 minus 1981–2010); for total wetday rainfall amount (PRCPTOT; first row), wet‐day frequency (RR1; second row), wet‐day intensity (SDII; third row), dry spells (CDD; fourth row) and total wet‐day rainfall above the 95th percentile (R95PTOT; fifth row), from RCM ensemble mean experiments over Cameroon. Stippling indicates areas where the change is significant (i.e. where at least 80% of simulations agree on the sign of the change).

Abstract. The impact of direct-seeding mulch-based cropping systems (DMC), direct seeding (DS) and tillage seeding (TS) on Sorghum yields, soil fertility and the rehabilitation of degraded soils was evaluated in northern Cameroon. Field work consisted of visual examination, soil sampling, yield and rainfall data collection. Three fertilization rates (F1: 100 kg ha−1 NPK + 25 kg ha−1 of urea in DMC, F2: 200 kg ha−1 NPK + 50 kg ha−1 of urea in DMC and F3: 300 kg ha−1 NPK + 100 kg ha−1 of urea in DMC) were applied to each cropping system (DS, TS and DMC), resulting in nine experimental plots. Two types of chemical fertilizer were used (NPK 22.10.15 and urea) and applied each year from 2002 to 2012. Average Sorghum yields were 1239, 863 and 960 kg ha−1 respectively in DMC, DS and TS at F1, 1658, 1139 and 1192 kg ha−1 respectively in DMC, DS and TS at F2, and 2270, 2138 and 1780 kg ha−1 respectively in DMC, DS and TS at F3. pH values were 5.2 to 5.7 under DMC, 4.9 to 5.3 under DS and TS, and 5.6 in the control sample. High values of cation exchange capacity were recorded in the control sample, TS system and F1 of DMC. Base saturation rates, total nitrogen and organic matter contents were high in the control sample and the DMC than in the others systems. All studied soils were permanently not suitable for Sorghum due to the high percentage of nodules. F1 and F2 of the DS were currently not suitable, while F1 and F3 of DMC, F3 of DS and F1, F2 and F3 of TS were marginally suitable for Sorghum due to low soil pH values.