MEKARN Conference 2010
The “biotest” method was used to evaluate the effect of biochar from a gasifier stove on growth of maize in acid (pH 4) and neutral (pH 7) soils. Six levels of biochar (0, 1, 2, 3, 4 and 5%) in presence (50 kg N/ha over 35 days) or absence of biodigester effluent were evaluated in a random block factorial design (6*2*2) with 4 replications. The biochar was derived by gasification of rice husks in an updraught (TLUD) stove, and contained 35% ash and 65% carbon.
When no effluent was added the height of the maize in the acid soil after 42 days increased with a curvilinear trend according to level of biochar, the maximum response being with 3% biochar (Figure 1). In the neutral soil there was a slight increase from zero to 1% of biochar but no effect at higher levels. When effluent was added (Figure 2) there was no effect of the biochar on maize growth in the neutral soil and only a slight increase from zero to 1% biochar in the acid soil.
Effects on the growth of green biomass (leaf + stem) showed similar trends but the effects being more pronounced. In acid soil with effluent, the addition of 2% biochar tripled the biomass yield; without effluent, 3% of biochar quadrupled the yield. In neutral soil with effluent there was no effect on biomass yield due to biochar. However, in the absence of effluent, the biomass yield was doubled by addition of 2% biochar.
|Figure 1. Effect of biochar on maize growth in acid soil (pH 4.0) with and without effluent||Figure 2. Effect of biochar on maize growth in neutral soil (pH 7.0) with and without biodigester effluent|
|Figure 3. Effect of biochar on maize biomass in acid soil (pH 4.0) with and without effluent||Figure 4. Effect of biochar on maize biomass in neutral soil (pH 7.0) with and without effluent|