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Access to information on soil nutrients status and variability is essential in understanding the potential of soils and their responsiveness to management interventions in agriculture. The current study evaluated soil nutrients status in selected agroecological zones (AEZs) of Cameroon and identified variations and their adequacy for maize (Zea mays L.), sorghum (Sorghum bicolor L. (Moench)), and cassava (Manihot esculenta Crantz) production. A total of 163 soil samples were collected from surface (0–15 cm) layer for the determination of pH, organic matter (OM), estimated nitrogen release (ENR), sulphur (S), calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), boron (B), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), aluminium (Al), phosphorus (P), total exchangeable capacity (TEC), and base saturations. The results showed different degrees of variability in soil nutrients ranging from low to very high in all the AEZs. The soils in all the AEZs were consistently deficient in available phosphorus, sulphur, boron, and zinc in varying proportion and might be inadequate to supply cultivated maize, sorghum, and cassava with the nutrients needed to achieve optimal growth. The soils were also prone to Mg-induced K deficiency, which could limit the growth of maize, sorghum, or cassava. These results therefore suggest that management of inherent soil properties should be based on-site specific situations.

This paper deals with the physical characterization and the optimization of fineness moduli of some natural sand samples for their appropriate valorization in construction in North Cameroon. Five sands samples (SN5, SB1, SB2, SB3 and SB4) were selected from various locations. Tests conducted include Particle size analysis, Organic impurities, Sand Equivalent and Bulk density. Fineness Modulus (FM), Mean grain, Sorting index (Si), Skewedness index and Uniformity coefficient have been deducted mathematically. Results shown that the particle size distribution curves of the studied sands have an "S" shape. The sand equivalent values vary between 91.1 and 96.8 %, characteristic of very clean sand. The fineness moduli values vary between 1.9 and 3.4 except for samples SB1 and SB2 which are coarser with values of 3.4 and 3.3 respectively. Others results shown that all the sands are pure (impurity level less than 0.5 %), well classified Sorting index Si < 0.35) and Coefficient of uniformity (Cu < 2). Studied sands are globally coarse (skewedness index between -0.35 at -0.79F). Only SB4 and SN5 satisfy the NF EN 933-1 gradation limits. Combinations of SB3 (FM = 2.1) with SB1 (FM =3.4) or SB2 (FM= 3.3) were carried out to get desired sand gradation (2.2 to 2.8), SB4 and SN5 having already good fineness moduli of 2.6 and 2.8 respectively.