Treatment effect on soil water hydraulic properties: Generally,
biochar amendment improved sandy soil hydraulic properties.
Saturated hydraulic conductivity (Ks) of treatments is presented
in Table 2 while the soil water retention and estimated unsaturated
hydraulic conductivity are shown in Figs 1 and 2, respectively.
The results show that T500M20 reduced hydraulic conductivity
geometrically as compared to control. Thus, we can conclude
that biochar produced at 500°C had the highest effect on the rate
of water movement within the soil.
Soil hydraulic parameters showed that saturated water content
θs ranged from 0.406 to 0.634 for control and T500M20,
respectively (Table 2). Saturated water contents of T500M20 were
56% higher than that of control. Soil water retention curves are
presented in Fig. 1. It can be observed that biochar improved
water retention relative to control, and this is in line with previous
studies where charcoal addition at 45 and 1000 Mg ha-1 rate
increased water retention in sandy soil 13, 15. However, it has to be
noted that 45 and 1000 Mg ha-1 were much higher than the rates
used in this work. Generally, all treatments significantly retained
more water than control until pF2.7 except for T400M10 which did
not show water retention difference from pF1.2 down to saturation
pF0 when compared to control, and T500M20 which retained more
water than other treatments way up to pF3.3. Biochar significantly
increased the available water capacity (AWC) of all treated sand