Influence of Biochar and Irrigation on Crop Production in the Coastal Savannah Zone of Ghana

Abstract

A study was conducted during the major growing seasons of 2015 to 2017 to determine the integrated impact of corn cob biochar and irrigation on the growth and yield of maize, cowpea and tomato in the coastal savannah zone, Ghana. Preliminary pot experiments were set up to determine the appropriate biochar rates, biochar particle sizes and fertilizer to be used in subsequent field experiments. Completely randomized design with 4 levels of biochar (0, 20, 40, 80 t ha-1), 2 levels of biochar particle sizes (< 2 mm and 2-4 mm) and 2 levels of irrigation regimes (full and deficit) was used. Irrigation generally did not have significant effect on maize growth. However, an increase in biochar significantly increased the fresh and dry above-ground biomass of maize. Generally, the < 2 mm biochar particle size improved maize growth compared to the 2-4 mm biochar particle size. There was a significant interactive effect of biochar rate, biochar particle size and irrigation on the above-ground biomass of maize. There was an increase in growth when phosphorus was loaded with biochar before application, compared to when phosphorus was applied in the form of NPK. Split plot design was used for the field experiments with irrigation and biochar as the main and sub-plots, respectively. There were 3 levels of irrigation (full, deficit and no irrigation) and 3 levels of biochar (0, 10, 20 and 20+P t ha-1 and 0, 20, 40 and 40+P t ha-1) in 2016 and 2017, respectively. The results indicated that an increase in biochar significantly increased leaf area, leaf area index, above ground biomass and yield of maize. For instance, in 2016 maize yield obtained from plots treated with 20+P t ha-1 biochar was 8.1 t ha-1, i.e. five times higher than yields from the control plots. Cowpea yield also increased with increasing rates of biochar. Full and deficit irrigation significantly improved maize growth and yield of maize and cowpea. In general, biochar treatments ladened with phosphorus performed better for maize, cowpea and tomato. There was a strong and positive correlation between maize grain yield and crown root diameter. An increase in biochar rate increased tomato fruit yield. Biochar and irrigation did not signficantly affect the quality of tomato fruits. Therefore, soil amendments with biochar, especially loading it with phosphorus before incooperating it in the soil and with supplemental irrigation even in the dry season, crop growth and yield will improve.