Water Retention of Biochar Amended Soils.

We analyzed the water holding capacities of soils amended with biochars made from switchgrass, pecan shells, peanut hulls, poultry litter, and hardwood sawdust. Soils were amended with 20 g/kg (44 tonnes/ha) of each biochar produced at both high (>500 degrees C) and low (<400 degrees C) temperatures. Amended soils (450 g packed to a bulk density of 1.2 g/cc) were incubated for 60 days in 10-cm diameter, 9-cm deep pots with a 20 mesh nylon screen on the bottom to prevent soil loss from drain holes. Treatments were maintained at 10% soil water content on a dry weight basis by weighing and adding water to pots 2 to 3 times a week. The total amount of water added was treated as a surrogate for water holding. Water holding capacities were also measured in a ku-pF apparatus (UGT GmbH, Müncheberg, Germany) using duplicate samples that were prepared separately at the beginning of the experiment. Preliminary results show that most treatments held more water than the control and high-temperature biochar water holding capacities correlated negatively with water added to the soil during incubation.