Location: Northwest Irrigation and Soils Research
Title: Low-Temperature Biochar Affects an Eroded Calcareous Soil Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 2012
Publication Date: N/A
Technical Abstract: Previous research showed little benefit from using a high temperature, high pH biochar for improving the fertility of eroded calcareous soils. We thus explored the potential of an activated, low-temperature, low pH biochar to improve their fertility status. In a microcosm study conducted at 20 degrees Celsius, increasing amounts of a steam-activated, low temperature (350 degrees Celsius), low pH (5.8) switchgrass biochar (0, 1, 2, or 10 percent by weight) were mixed into an exposed calcareous soil (pH 8.3). Microcosms were bought to field capacity twice per week with reverse osmosis water, and then destructively sampled at 1, 2, 3, 4, 5, and 6 months. Soil pH, nitrate-nitrogen, Olsen-extractable phosphorus, plant-available nutrients, total carbon and nitrogen, organic carbon, and substrate induced carbon dioxide respiration were measured. Increasing biochar application rate caused a decrease in soil pH, nitrate-nitrogen concentration, and extractable copper, alongside increases in total carbon and nitrogen content, organic carbon content, Olsen-extractable phosphorus, substrate induced respiration, and plant-available iron, manganese, nickel, and zinc content. The reduction in soil nitrate-nitrogen concentration, coupled with the increase in organic carbon content and an increase in the carbon/nitrogen ratio, suggested that nitrogen immobilization was occurring. The increase in extractable zinc suggests that this biochar may help overcome zinc deficiencies in exposed calcareous subsoil, but the material has the potential to cause plant copper deficiencies. Over time, soil pH and nitrate-nitrogen concentration generally decreased, while the organic carbon content remained elevated. When added to exposed calcareous subsoil, steam-activated, low temperature switchgrass biochar application may improve the short-term micronutrient status and can increase the soil carbon content; yet excessive biochar applications may cause reductions in soil nitrate-nitrogen and plant-available copper.