Effects of three different biochars amendment on water retention of silty loam and loamy soils

A greenhouse experiment was conducted to investigate the effects of three biochar types on available water contents (AWC) of sandy loam and loamy soils. Two soil types, three different biochar types (BT), five biochar rates (BR) and five fertilizer levels (FR) were included in the study. The biochar types were produced from rice husk (RB), bean harvest residue (BB) and corn cobs (CB). All of the biochar types were either saturated with nutrient rich dairy effluent (DE) or kept unsaturated, while the soils with no addition of biochar types were regarded as control treatment. Winter wheat (Triticum aestivum L.) was grown for two seasons and soil sampling was done following each harvest. The mineral fertilizers were applied at the beginning of each season, while biochar types were applied only at the beginning of the experiment. Soil samples were analyzed for total porosity, water contents at field capacity and permanent wilting point, and thereby AWC was calculated. Soil type, BT, BR and FR had significant effect on water retention and total porosity. In both soil types, total porosity was significantly lower at higher BRs than control. The addition of different biochar types continually increased the AWC both in sandy loam and loamy soils, though the effect was more obvious in the loamy soils. However, comparing the water retention with 2.0 and 3.0% BR relative to the control in the first season, the increase rate of AWC was much higher in sandy loam soil compared to loamy soil. The aging of all three biochar types in second season caused to increase in AWC at a rate of 19.9% in RB, 6.0% in CB and 6.1% in BB. The results revealed that all biochar types used in this experiment can be utilized to improve AWC in both sandy loam and loamy soils.