Impact of land management system on crop yields and soil fertility in Cameroon

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.