Comparative Effects of Basalt Dust, NPK 20-10-10 and Poultry Manure on Soil Fertility and Cucumber (<i>Cucumis sativus</i>) Productivity in Bafut (Cameroon Volcanic Line)

Abstract

Although chemical fertilizers have boosted food production in the last century, their efficiency is limited by their low potential to remineralize and restore chemically depleted soils at long term. This work investigates the comparative effects of basalt dust, poultry manure and NPK 20-10-10 on soil fertility and cucumber performance in Bafut (North-West Cameroon). The work was done in the field and in the laboratory. The experimental plot (82 m 2) was a randomized complete block design (RCBD) with five treatments (and three replications): control (T 0), 2.5 tons ha-1 of basalt dust (T1), 20 tons ha-1 of poultry manure (T 2), 0.7 tons ha-1 of NPK 20-10-10 fertilizer (T 3) and 5 tons ha-1 of basalt dust (T 4). The main results revealed that T 0 showed a sandy clayey loam texture, acidic pH (5.1), very high organic carbon (6.4%), low total nitrogen (0.2%) and moderately available phosphorus (16.70 mg kg-1). The exchangeable complex revealed high K (1.02 cmol (+). kg-1), very low Ca (0.45 cmol (+). kg-1) and Mg 2+ (0.17 cmol (+). kg-1), low Na + (0.2 cmol (+). kg-1), very low sum of exchangeable bases (1.84 cmol (+). kg-1), very low cation exchange capacity (CEC) and a moderate base saturation (43.4%). The C/N was very high (23) indicating very poor quality organic matter and a potentially very slow mineralization rate. After treatment, pH, exchangeable bases Ca and Mg increased after harvest whereas Na and K decreased for all the treatments. The growth and yield parameters of all treatments, except number of fruits, were such that T 2 >T 3 >T 4 >T 1 >T 0. The numbers of fruits were as follows: T 2 >T 4 >T 3 >T 1 >T 0. The most economically viable soil treatment was attained by T 2 with a profit rate (PR) of 933% and a VCR value of 10.3. Treatments T 1 , T 2 , T 3 and T 4 were all profitable since their value-to cost ratio (VCR)>1, but only T 2 and T 3 show a VCR (value-to-cost ratio) greater than 2 and are thus recommended for popularization.