Study of the Effect of Biochar Incubation on Some Physico-Chemical Properties of a Tropical Leached Soil from South-West Chad

Soils in the Sudanian zone of Chad, and more specifically leached tropical soils, were subject to physical and chemical degradation phenomena that hamper crop production. Solving this problem requires solutions for the rational improvement of fertility. The aim of this study, conducted in a controlled environment, was to assess the fertilising potential of biochar on impoverished soil by monitoring the kinetics of the evolution and release of chemical elements that improve the physico-chemical quality of the soil. Four treatments were carried out: control soil (T0), treatment 1B: 100g soil + 0.225g biochar (i.e. 5 t/ha), treatment 2B: 100g soil + 0.3375g biochar (i.e. 7.5 t/ha) and treatment 3B: 100g soil + 0.450g biochar (i.e. 10 t/ha). Each treatment was repeated four times. Four main parameters were measured during the trial period: pH, assimilable phosphorus, exchangeable bases and their sums (Ca, Mg, K, Na and SBE) and cation exchange capacity. These different parameters showed that the biochar treatments significantly improved soil quality, whatever the dose and incubation time, compared with the T0 control. Treatment 1B (5t/ha biochar application) increased pH by an average of 6.5%, phosphorus by 132.5%, SBE by 406.1% and CEC by 43.4%. Treatment 2B (application of 7.5 t/ha of biochar) improved pH by an average of 8.5%, phosphorus by 155.1%, SBE by 207.6% and CEC by 46.2%. Treatment 3B (application of 10t/ha of biochar) produced a marked improvement, increasing pH by 11.2%, phosphorus by 198.7%, SBE by 457.6% and CEC by 29.9%. These results further confirm the vital importance of biochar in fertilising impoverished tropical soils. Based on pH, sum of bases and phosphorus, treatment 3B gave better results by considerably increasing the initial chemical element content of the control soil than the other biochar treatments.