Long-Term Influences of Biochar, Manure, or Sawdust Additions on Nutrient Leaching in Calcareous Soil.

Additions of organic materials to eroded calcareous soils have been suggested as a means of increasing nutrient availability to crops and a way to increase soil carbon storage. Due to its more recalcitrant nature, the organic C in hardwood-derived biochar (73% C, 15% ash) may produce different and more long-lasting effects on nutrient availability than more degradable organic-C sources. An outdoor, 5-y pot study compared the effect of a one-time application of four amendments (biochar, dairy manure, sawdust, or acidified sawdust, each applied at three rates: 0, 1, and 2% by mass) to a calcareous, silt loam subsoil. Pot soils were tilled by hand to 15-cm depth in spring and planted to one of the local crops. Pots were drip-irrigated to minimize leaching during the growing season. Once each spring and fall, an average 650 mL of leachate was collected from each pot in response to an excess application of irrigation water. In the leachate, we measured the pH, electrical conductivity, dissolved organic C, inorganic N, Cl, and ICP-measured Al, Ca, Fe, K, Mg, Mn, Na, P, S, Zn concentrations. This report will discuss treatment effects on the leachate nutrient parameters.