Effect of Different Biochars Application on Some Soil Properties and Nutrients Availability in a Calcareous Soil

Plant residue pyrolysis and its conversion to biochar for soil application may improve some soil properties, as well as carbon sequestration and air pollution reduction. The purpose of this investigation was the evaluation of the effect of five kinds of biochar on some properties of a calcareous soil. The used biochars were produced from pyrolysis of residues of wheat, maize, cotton, sesame, and maize cobs at 500 °C for three hours under limited oxygen condition. Then, the effect of 2% biochar application to a calcareous soil was studied in a randomized complete block design with three replicates. Soil samples were incubated at 22±2 °C and 50% of saturated moisture content for 90 days. Then, soil properties including pH, electrical conductivity, cation exchange capacity, and organic carbon as well as potassium pools distribution, total N, and available P, Fe, Mn, Zn, and Cu were determined. Results indicated that cotton and sesame biochars significantly increased soil pH. All biochars increased soil OC and EC, significantly. Soluble, exchangeable and non-exchangeable potassium were affected by biochars application and its kind. Biochars increased soluble K by 4.4 to 7 times. Increase in exchangeable K was from 144 to 209 mg kg^-1 for cotton and sesame biochars application, respectively. Non-exchangeable K was also increased from 290 to 532 mg kg^-1. Availability of N, P, Zn, and Cu was not affected by biochar application, but cotton and sesame biochars increased available Fe. Available Mn was also increased by all biochars. With respect to considerable increase in different K forms by biochar application and considering K deficiency problem in some calcareous soils of southern parts of Fars province, use of biochar as a K-rich component in K fertility management may be recommendable.