The characteristics of Ultisols in Kalimantan are acidic soil pH (pH <5), high Al saturation and low organic matter content. The application of organic matter into the soil can improve the chemical properties of Ultisols. It is hoped that the provision of biochar corn cobs can be an alternative to improve the soil properties of Ultisols. This study aims to determine the effect of corn cob biochar and cow manure on pH, CEC, Al-dd concentration, and the total population of bacteria in Ultisol soil. This study used a single factor completely randomized design (CRD) consisting of 10 treatment levels (K= control, A1 = Biochar 2 tons h^-1, A2 = Biochar 4 tons h^-1, A3 = Biochar 6 tons h^-1, A4 = Cow manure 2 tons h^-1, A5 = Cow manure 4 tons h^-1, A6 = Cow manure 6 ton h^-1, A7 = Biochar 2 tons h^-1 + Cow manure 1 ton h^-1, A8 = Biochar 4 tons h^-1 + Cow manure 1 ton h^-1, A9 = Biochar 6 tons h^-1 + Cow manure 1 ton h^-1. Each treatment with 3 replications.  The results showed that the effect of biochar and cow manure had a significant effect on pH, Al-dd concentration, CEC and total bacterial population in Ultisol soil. Biochar treatment with a dose of 6 ton ha^-1 is the best treatment to increase pH, CEC and decrease Al-dd. The highest total bacterial population was obtained by biochar treatment dose 6 ton ha^-1 + cow manure 1 ton ha^-1.

Keywords: 

Biochar; Corncob; Cow manure; Ultisol; Bacteria.