Effect of Amending Acid Oxisols Using Basalt Dust, Tithonia diversifolia Powder and NPK 20-10-10 on Garlic (Allium sativum) Production in Bafut (Cameroon Volcanic Line)

Aims: To compare the effects of basalt dust, Tithonia diversifolia (T. diversifolia) powder and NPK 20-10-10 on the growth and production of Garlic (Allium sativum, softneck variety) in Bafut (Cameroon Volcanic Line).

Study Design: A randomized complete block design (RCBD) with three replications in the field was used. The treatments were T0 (control), T1 (0.7 tons ha-1 NPK 20-10-10), T2 (0.4 tons ha-1 basalt), T3 (0.6 tons ha-1 basalt) and T4 (0.5 tons ha-1 T. diversifolia powder).

Place and Duration of Study: The study conducted in Bafut (Cameroon) from 2nd August 2017 to 24th February 2018.

Methodology: Fieldwork involved land preparation, planting and collection of growth and yield parameters as well as rocks and soil sampling. Laboratory work involved soil physicochemical analysis and cutting of rock thin sections for microscopic observations. The plant data were subjected to statistical and economic analyses.

Results: The control soil (T0) showed a sandy clayey loamy texture, acidic pH (5.1), very high organic carbon (6.4%), low total nitrogen (0.2%) and moderate available phosphorus (19.42 mg kg-1). The exchangeable complex revealed high K+ (0.88 cmol (+).kg-1), very low Ca2+ (0.63 cmol (+).kg-1) and Mg2+ (0.21 cmol (+).kg-1), low Na+ (0.07 cmol (+). kg-1), very low sum of exchangeable bases (1.79 cmol (+).kg-1), moderate cation exchange capacity (CEC) (22.7 cmol (+). kg-1) and a very low base saturation (7.88%). C/N ratio was very high (35>17) indicating very poor quality organic matter and a potentially very slow mineralization rate. Growth and yield parameters, except fruit number, were such that T2>T3>T4>T1>T0. T2, T3 and T4 plants gave high yields while T1 recorded the lowest yields below the control. The net yield showed that T3>T4>T2>T0>T1 suggesting that basalt dust and T. diversifolia powder improved soil fertility that in turn boosted yields. Economically, T1 had a BCR (benefit-to-cost ratio)<1 indicative of no profit, while T2, T3 and T4 showed a BCR>2 indicating more than 100% profit of the investment and a possibility of popularization of these treatments.

Conclusion: Natural basalt dust and T. diversifolia powder treatments gave better garlic yields indicating a better soil fertilizing capacity compared to synthetic NPK 20-10-10. Basalt dust and T. diversifolia can be popularized to local inhabitants.