Chapter 5.
Conclusions and Recommendations5.1 P Fraction Distribution and Yield in Wafi SoilFrom the experimental results, it was uncovered that sole application of 15 t ha-1 biochar and its co-application with 64 mg kg-1 P fertilizer increased soil pH, inorganic aluminium, and calcium bound P, and soluble P however reduced iron bound P within short cropping period (30 days). Soil pH and the concentration of soluble P, inorganic iron and calcium bound P in biochar co-application with P fertilizer was higher than sole application of biochar on acidic soil. Inorganic aluminium bound P, however was higher in sole biochar application than its co-application with P fertilizer.In light of that, it was further disclosed that increase in soil pH and the concentration of inorganic aluminium and calcium bound P with sole application of biochar caused inorganic iron bound P and exchangeable Al and Ca cations to decrease thereby increasing soluble P. Comparably, it was unearthed that with the co-application of biochar and P fertilizer, soil pH and concentration of inorganic iron and calcium bound P increased while amount of inorganic aluminium P decreased to increase soluble P.
Soil pH and concentration of soluble P, inorganic iron and calcium bound P was also noted to be higher with this soil amendment in comparison to sole application of biochar. Moreover, it was also divulged that concentration of inorganic aluminium bound P with both soil amendments comparably was low indicating the efficiency of biochar and its co-application with P fertilizer to reduce adsorption of P on aluminol soil colloidal surfaces and thus aluminium toxicity.The study also unearthed that the sole effect of biochar and combined liming effect of biochar and P fertilizer does not last for longer cropping period (90 days), however faded as adsorption of P increases on aluminol and ferrol soil colloidal surfaces. Higher amount of inorganic aluminium P in both soil amendments indicated the persistence of aluminum toxicity as efficiency of the soil amendment to counter P fixation faded. Higher aluminium toxicity is eminent in combination of biochar with P fertilizer than sole application of biochar in acidic soil. It was further uncovered that sole application of biochar had higher ability to increase the concentration of P in plants than its co-application with P fertilizer, however recorded a lesser crop yield.
Co-application of biochar and P fertilizer, relatively, recorded a lesser concentration of P in plant however marked a higher crop yield than sole application of biochar because of added P and its ability to make remarkable improvements in P use and agronomic efficiency of the leguminous crop. For these reasons, conclusion can be made that the approach of co-applying biochar sourced from kunai grass feedstock through pyrolysis at 500 0C with P fertilizer in acidic soil to grow crops is beneficial and of paramount importance to counter P adsorption, improve soil fertility and crop yield so as to ameliorate food system to feed the increasing global population. 5.1 P Fraction Distribution and Yield in Bug SoilSole application of 15 t ha-1 on Bug soil increased soluble P significantly as concentration of calcium and aluminium bound P increases at day 30. Soil pH and concentration of inorganic iron bound P, however decreased.
Relatively, co-application of 15 t ha-1 with 64 mg kg-1 P fertilizer has shown to insignificantly increase soil pH and concentration of inorganic aluminium, iron and calcium bound P.Therefore, one can conclude that sole application of biochar had the ability to increase concentration of inorganic calcium and aluminium bound P, and reduce soil pH and inorganic iron bound P to increase soluble P in soil solution. Comparably, co-application of the biochar with P fertilizer by increasing soil pH and concentration of inorganic aluminium, iron and calcium bound P, can significantly increase soluble P.It was also uncovered that soluble P obtained with sole application of biochar was much lower than its co-application with P fertilizer. Further disclosure from the study noted that the higher concentration of inorganic calcium bound P than aluminium and iron P in alkaline soil showed inherent adsorption of P on calcite soil colloidal surfaces in alkaline soil.The study also revealed that mixture of biochar and P fertilizer had the ability to overcome P adsorption, nutrient stress, slow diffusion of available P, root induced acidification, root growth reduction and other problems associated with the bioavailability and acquisition of P based on the chemical and biological processes in the rhizosphere and therefore increased its P use and agronomic efficiency and thus concentration of P in the plant and crop yield significantly.
Sole addition of biochar, on the other hand, does not have the ability to increase P concentration in plant in alkaline soil though it can moderately increase crop yield.The study also unearthed that the liming effect of biochar does not last longer in an extensive cropping period (90 days) for both the sole biochar application and its co-application with P fertilizer. High concentration of calcium bound P indicated very high and inherent adsorption of P on calcite soil colloidal surface as effect of the soil amendment faded in the long run.For these reasons, conclusion can be made that the approach of co-applying biochar sourced from kunai grass feedstock through pyrolysis at 500 0C with P fertilizer in alkaline soil to grow crops is beneficial and of paramount importance to counter P adsorption, improve soil fertility and crop yield so as to ameliorate food system to feed the increasing global population. 5.
3 RecommendationsFrom the study findings, it is recommended that co-application of 15 t ha-1 and 64 mg kg-1 in acidic and alkaline soils respectively had very high potential in alleviating P fixation problems concurrently increasing crop yield. Further research with consecutive biochar co-application with P fertilizer after every 30 days infield is required to prove this scientific finding.
