A field trial was conducted to assess the effect of the application of pulverized rhyolitic materials and poultry manure on the yield of cabbages and soil chemicals in the locality of Bandjoun, west Cameroon. The treatment with rhyolitic rock materials combined with poultry manure portrayed the best yield (= 51 000 kgha-1) followed by the treatment with poultry manure alone (= 27 000 kgha-1). Lower yields were obtained from the treatment with rhyolitic rock materials alone (= 9 000 kgha-1) and the control (= 4 000 kgha-1). The combination of poultry manure and rhyolitic rock materials enhanced cabbage yield by 12.75 fold in relation to the control and rendered the soil less acidic (pH= 6.1). Soil chemicals also increased with the amount of basic ions (Ca + Mg + K) varied from 03.48 to 44.83 me/100g. Available P, total N and Organic Matter increased from 0.26 to 4.32, 0.20 to 0.36 and 2.60 to 11.21, respectively. Then, the amendment of these tropical soils with powders of rhyolite in addition to poultry manure demonstrated a significant increase in the yield of cabbages, major soil chemicals nutrients, organic matter and the soil acidity.

Keywords: rhyolitic powders, poultry manure, cabbage, yield, soil chemicals, soil acidity