Effect of Cow Manure Biochar Levels on the Amount of Spontaneously and Mechanically Dispersible Clays in Two Calcareous Soils with Different Textures at Different Times After Application

Considering that biochar is highly regarded as a soil conditioner, it is necessary to investigate its environmental effects and effects on soil properties, including clay dispersion. Dispersion of clay in arid and semi-arid regions, in addition to destroying soil resources, causes environmental pollution and increases soil erosion. For this reason, there is a need to overcome this problem with existing solutions. This study aimed to investigate the effect of the application of different levels (0, 1.5, and 3% wt) of cow manure biochar on the amount of spontaneously and mechanically dispersible clay and the mean weight diameter of aggregates (MWD) in two calcareous soils with different textures (clay loam and sandy loam) in periods of 40, 80, and 120 days after application. The results showed that the application of 3% biochar increased the spontaneously dispersible clay by 4.2%, as well as the levels of 1.5% and 3% of biochar increased mechanically dispersible clay compared to that of the control by 4.3% and 30.8%, respectively. The amount of mechanically and spontaneously dispersible clay increased over time. While the effect of soil texture on spontaneously dispersible clay was insignificant, the amount of mechanically dispersible clay in the clay loam soil was 61.2% more than that of the sandy loam soil. Results also indicated that addition of 1.5% and 3% of biochar decreased the MWD of aggregates by 24.2 and 20.6% in the sandy loam and 16.5 and 13.6% in the clay loam soils, respectively. The mentioned decrease in MWD caused an increase in dispersible clay. The results of this research can provide the necessary information regarding the effect of biochar on the amount of clay dispersion to recommend using biochar as a soil conditioner.