Assessing the Potential of Biochar In Increasing Water Holding Capacity of Sandy Soils.

Increasing water use efficiency on irrigated lands may be critical to provide enough food to feed an increasing global population. We hypothesize that biochar application to sandy soils will increase soil water holding capacity and that deep banding of biochar will increase water retention by sandy soils relative to uniform mixing of biochar with topsoil. We further hypothesize that the depth of biochar incorporation will influence the rate of biochar surface oxidation and hence moisture retention and cation exchange capacity of biochar amended soils. These hypotheses will be tested using soil incubations in 18cm height by 7.4cm diameter PVC columns. Biochar mixed with soil will be placed in either the bottom 11.4cm or the top 11.4cm of the columns, to simulate deep-banded in rows and uniform topsoil mixing applications, respectively. Three rates of biochar application, 0%, 3% and 6% (w/w) with 4 sets of 18 columns will be incubated at 30 °C and 80% RH. Every 7 days 150ml of 0.001M CaCl2 solution will be added to the columns to produce leaching. Sets of columns will be harvested after 24hs, 15 days, 29 days and 92 days. We will report the impact of incubation time and depth of biochar placement on gravity drained water retention, drainage, evaporation and ECEC.