An investigation of the effect of biochar application rates on CO2 emissions in soils under upland rice production in southern Guinea Savannah of Nigeria

John Olajide Olaniyan; Theophilus Olufemi Isimikalu; Bashiru Ademola Raji; Kehinde Olayemi Affinnih; Sikiru Yusuf Alasinrin; Olusegun Nathaniel Ajala

doi:10.1016/j.heliyon.2020.e05578

An investigation of the effect of biochar application rates on CO₂ emissions in soils under upland rice production in southern Guinea Savannah of Nigeria

Heliyon. 2020 Nov 25;6(11):e05578. doi: 10.1016/j.heliyon.2020.e05578. eCollection 2020 Nov.

Authors

John Olajide Olaniyan¹, Theophilus Olufemi Isimikalu¹, Bashiru Ademola Raji¹, Kehinde Olayemi Affinnih¹, Sikiru Yusuf Alasinrin¹, Olusegun Nathaniel Ajala¹

Affiliation

¹ Department of Agronomy, Faculty of Agriculture, University of Ilorin, Ilorin, Kwara State, Nigeria.

Abstract

Biochar is a chemically recalcitrant carbon-rich solid material used in soil for its potential to improve soil quality and sequester carbon. While the rate of application has implications for soil carbon dioxide (CO₂) emission and the overall benefits of biochar, its effects are yet to be fully understood. To evaluate the effect of application rates of rice husk biochar on CO₂ emissions, 91-day field experiments were conducted on three soil types (Anthraquic Ustorthent, Grossarenic Kandiustalf, and Ustic Quartzipsamment) in the southern Guinea Savannah of Nigeria, using three biochar application rates of 5, 15 and 25 t h^-1, and control. A two-way ANOVA showed that cumulative CO₂ emissions were significantly (p < 0.01) different between soil types and treatments, and soil type/treatment interactions were also significant at p = 0.05. The highest cumulative CO₂-C emission of 2.77g/m² was recorded in the Grossarenic Kandiustalf, while the least value of 2.11g/m² was recorded in the Ustic Quartzipsamment. CO₂ emission increased with increasing biochar application rates, with the highest (3.06 CO₂-C g/m²) value recorded at 25 t/ha compared to 2.78 g/m² and 1.52 g/m² values recorded for 5 t/ha and control treatments respectively. While CO₂ emissions increased with biochar application rate however, the percentage of biochar-C mineralized was higher at lower biochar rates, and differences were significant at p = 0.01. While 0.63 % of biochar C was mineralized under 5 t/ha biochar treatment, 0.15 % was recorded for 25 t/ha treatment. Factors that had significant correlation with CO₂-C emission in the soils were biochar addition rate, soil pH, N, P, Ca, Mg and K. At day 91, there were no significant differences in CO₂ emissions between amended treatments and control, and only a small percentage (<1) of biochar C had been mineralized.

Keywords: Agricultural soil science; Biochar; C mineralization; CO2 emission; GHGs; Rice; Soil composition; Soil health; Soil quality; Soil science.