Foumban is located in the West Cameroon Highlands, precisely in the Noun Valley. Given the low productivity recorded in this locality, this study aims to assess the state of soil fertility in this locality in order to redefine the major agro-ecological complexes in Cameroon. In order to achieve this objective, ninety (90) soil samples of this area were studied in order to determine their physicochemical parameters, namely, soil organic carbon (OC), total nitrogen (N), available P, total P, exchangeable cations (Ca, Mg, K, and Na), cation exchange capacity (CEC), and pH of water. The results obtained showed that the soils of Foumban present three classes of fertility, namely: class one (01) includes soils with a good level of fertility that are plaggic hortic NITISOLS (arenic) (NIpha), the chernic arenic UMBRISOLS (UMca), umbric arenic FERRALSOLS (Flua), mollic fragic NITISOL (hortic) (NImfh), the cambic hortic FERRALSOLS (plaggic) (FLchp) on basalts, umbric pisoplinthic PLINTHOSOLS (haplic) (PLuph), nitic CHERNOSOLS (pretic) (CHnp), and cambic FRAGISOLS (plaggic) (FGcp) with an area of about 528.71 Km2. Class two (02) includes soils with an average level of fertility that are the pretic UMBRISOLS (UMp) only, on an area of about 226.14 Km2. Class three (03) includes soils with a poor level of fertility that are the hortic FERRALSOLS (plaggic) (FLchp) on trachytes and the cambic FRAGISOLS (plaggic) (FGcp) with an area of about 38.47 Km2. Principal component analysis (PCA) has revealed that the parameters that control fertility in Foumban soils are C/N, pHeau, Ca, CEC, OM, P, and Mg. An amendment of these soils in organic fertilizer (fluent, compost, and manure) would facilitate the formation of the clay-humus complex; thus, allowing good retention of water in the soil.

Foumban, located in the Noun valley in western Cameroon, is a prime location for food production. However, this locality is experiencing a significant decline in productivity due to the acidity of its soil. This acidity is linked to the behaviour of certain soil properties essential for plant growth. The present work aims to study the behaviour of pH as a function of certain chemical parameters such as CEC, organic matter, exchangeable bases, and exchangeable aluminum and to map the spatial structure of the pH parameter by kriging. To achieve this objective, ninety soil samples were taken in the locality of Foumban and sent to the soil laboratory where physicochemical analyses were carried out. The results obtained were processed by statistical and geostatistical software. This made it possible to establish relationships between pH and other soil properties. The obtained R2 results show that pH-exchangeable aluminum and pH sum of bases are strongly correlated while pH-CEC and pH-organic matter are weakly correlated. For the spatial distribution of pH, the Gaussian model was applied to fit the experimental semivariogram. The low values of the semivariogram of the pH-water contents obtained overall reflect a strong correlation of the values. The spatial structure obtained after kriging defines two groups of soils in the study area according to their acidity: acidic soils which cover about 82.4% of the study area and moderately acidic soils which occupy about 17.6% of the study area. Finally, it appears that acidity remains a real problem for the soils of Foumban. The risks of aluminum toxicity should not be overlooked. The rate of use of ammonia fertiliser in the study area should be reduced, especially in soils with a pH below 5.4. The use of strong base inputs such as calcium carbonate (CaCO3) or calcium hydroxide (Ca (OH)2) at normal doses is strongly recommended in acid soils.