Short-Term Effects of Biochar or Other Organic Amendments On Soil Water Retention.

Additions of organic materials to calcareous soils have been suggested as a means of increasing soil water holding capacity and a way to increase soil carbon storage.  Because of its porous physical structure, we hypothesized that the addition of biochar (hardwood derived, 73% C, 15% ash) would increase soil water retention as effectively as manure or sawdust amendments.  A pot study compared the effect of four amendments, biochar, dairy manure, sawdust, and acidified sawdust, all applied at three rates of 0, 1, and 2% to a highly calcareous, silt loam soil.   We collected disturbed samples of the intial soil-amendment mixtures and used a tension plate and pressure membrane apparatus to measure water retention at eight soil water potentials from -0 to -1.5 MPa.  This report will discuss treatment effects on soil water retention for these initial measurements.