The study was conducted in the locality of Dimbokro (6˚38'48'' North and 4˚42'18'' West), during the 2020 and 2021 cropping seasons (Figure 1). The region has a humid tropical climate, with a very hot, dry period (November to February) and a long rainy period (March to October). Over the last ten years, the average annual temperature has risen from 31˚C to 37.1˚C, and even 49˚C in the hot season (February-March) [2] . Islets of forest and savannah [3] coexist and are mainly underlain by Birimian schists [4] . Intensive cocoa and coffee monocultures have largely contributed to accentuating the acidic conditions of the environment, modifying soil structure and depleting the soil of nutrients [5] .

Table 1 shows the average proportions (%) of sand, silt and clay in forest and savannah soils. In forest and savannah zones, sand, silt and clay contents are significantly different. In both forest and savannah soils, silt occupies almost half the mass of fine soil (45.87% - 53.52%). Sand and clay are moderately represented by medium to low contents, with a slight increase in clays at the expense of sands in the forest zone.

Table 2 shows the average contents of organic matter (OM), nitrogen (N) and the C/N ratio. Nitrogen is well represented in forest soils (0.07%) than in savannah soils (0.04%); (p = 0.0001). Organic carbon (C) concentrations recorded in forest and savannah soils indicate soils 2 to 3 times lower in organic matter. At all the sites studied, the ratio of carbon (C) to nitrogen (N) concentrations in savannah and forest soils was around 15.

Average soil K⁺, Na⁺, Ca²⁺ and Mg²⁺ contents in forest and savannah soils are shown in Table 3. Overall, differences in content were noted according to vegetation type. Except for sodium (Na⁺) (p ≥ 0.05), soils under forest are more enriched (p ≤ 0.05) in K⁺, Ca²⁺ and Mg²⁺ than those under savannah. Ionic equilibrium ratios in the soils, all below 1, are similar from one zone to another, except for K⁺/Mg²⁺, which is almost 2 times greater in the forest.

The characteristics of adsorbent complexes in forest and savannah soils include

P-minérales: mineral particles; E-T: standard deviation; Pr > F: probability threshold. In the same line, mean contents with the same letter (a or b) are identical. On the contrary, they are different with a < b at the 5% threshold.

E-C: chemical elements; E-T: standard deviation; Pr > F: probability threshold. In the same line, mean contents with the same letter (a or b) are identical. On the contrary, they are different with a < b at the 5% threshold.

pH, cation exchange capacity (CEC), base saturation rate (V) and sum of exchangeable bases (S) (Table 4). Soils are acidic in savannah zones (pH = 5.8) and very acidic in forest zones (pH = 5.1). CEC (8.87 vs. 3.57) and S (1.62 vs. 1.22) values are higher (p ≤ 0.05) in forest soils than in savannah soils, while adsorbent complexes appear more saturated with exchangeable bases in savannah soils (p ≤ 0.05).

In both forest and savannah zones, silt occupies almost half of the fine soil mass. Sand and clay are moderately represented. Soils are highly susceptible to capping [10] . In these areas, even the slightest rainfall is enough to make the soils very loose, more or less asphyxiating on the surface [11] , as evidenced by the recorded capping indices, which appear to be very unfavorable [12] . Similarly, the predominance of silts exposes the soils of this locality to water erosion with loss of nutrients, as noted by Quittet in 1967.

P-C: paramètres chimiques; E-T: standard deviation; Pr > F: probability threshold. In the same line, mean contents with the same letter (a or b) are identical. On the contrary, they are different with a < b at the 5% threshold.

p-Chimiques: chemical parameters; E-T: standard deviation; Pr > F: probability threshold. In the same line, mean contents with the same letter (a or b) are identical. On the contrary, they are different with a < b at the 5% threshold.

Average nitrogen contents in forest and savannah soils of less than 1% to 2% appear low, indicative of nitrogen (N)-depleted soils [13] . Compared with normal levels in tropical soils [1.6% - 1.75%] [13] , organic carbon (C) concentrations in forest and savannah soils indicate soils 2 to 3 times lower in organic matter (OM) [14] . This shows soils in conditions of low OM decomposition [15] , justified by calculated C/N ratios above 15. Scarce rainfall and rising soil temperatures are factors that influence OM decomposition and the availability of nutrients such as N [16] .

Except for sodium (Na⁺) (p ≥ 0.05), soils under forest are more enriched (p ≤ 0.05) in K⁺, Ca²⁺ and Mg²⁺ than those under savannah. Ionic balance ratios in soils, all below 1, are satisfactory [17] , indicating a better balance between soil nutrients, apart from that of K⁺/Mg²⁺, which is almost 2 times greater in forest soils. In soil situations where the observed K⁺/Mg²⁺ ratio is greater than 2, the response to magnesium fertilization is systematic. Potassium uptake by crops decreases, while magnesium uptake increases [18] .

The CEC and S values obtained (p ≤ 0.05) for forest and savannah soils compared with normal literature levels [19] are considered low. In addition, Dimbokro soils show severe limitations [20] due to CEC, which is low in forest zones and very low in savannah zones.

This results in very limited nutrient fixation on the adsorbent complex [20] , justifying the low exchangeable base saturation rates recorded. pH values of around 5.5 provide the conditions for the fixation of sesquioxides, notably aluminum, manganese etc., on the clay-humus complex, with probable crop toxicity [16] , one of the probable reasons for the drop in harvests observed among farmers in the area.