Impact of biochar, bentonite, and compost on physical and chemical characteristics of a sandy soil

In this study, bentonite (Ben), compost (Com), and biochar (Bio) were used as soil amendments to enhance sandy soil physical properties. A soil column experiment was conducted in a laboratory. Application rates were 3% (weight/weight) of Bio (T-1), Ben (T-2), and Com (T-3). Furthermore, mixtures 1.5% and 1.5% of Bio and Ben (T-4), Ben and Com (T-5), and Bio and Com (T-6), and a mixture 1%, 1%, and 1% of Bio, Ben, and Com (T-7) in addition to control treatment were adopted. The mixtures of amendments and sandy soil were concentrated at the top 10cm of columns. Results revealed that the cumulative evaporation was reduced by 2.3% and 5.7% as a result of using T-3 and T-5, respectively. However, the remaining treatments enhanced the cumulative evaporation. The application of amendments increased the capacity of the soil to maintain water by 35.4%, 24.4%, 13.3%, and 10.2%, for soils treated with T-5, T-3, T-7, and T-4, respectively. The water content at field capacity had the highest increase in the top 10cm when treatment T-3 was used. Although T-3 (compost) was the most efficient for enhancing soil physical properties, this study recommends T-5 and T-7 to improve hydraulic properties of sandy soils. This is due to the fact that biochar and bentonite remain in the soil for a longer period and resist biodegradation while compost overcomes the negative impact of soil chemical properties as a result of biochar and bentonite additions.