The effect of bio-char on soil properties and corn grain yields in Iowa

Abstract

<p>An incubation study was conducted to study the effect of three different types or "qualities" of nitrogen-enriched bio-char on total nitrogen (N), extractable phosphorus (P), extractable potassium (K), nitrate-N, ammonium-N, pH, SOM, and total organic carbon (C) in two soils. The different "qualities" represent the bio-char created with three different amounts of atmospheric air (0, 10, and 25%) present in the pyrolysis reactor when the bio-char was created. A field study was conducted to study the effect of N-enriched bio-char on corn grain yields, biomass yields, and soil ammonium (NH4₄⁺-N) and soil nitrate (NO₃^--N) concentrations. The incubation study occurred in a lab for eight weeks and the field study was conducted on one site from 2007 through 2008. The incubation study used a Nicollet surface soil (fine-loamy, mixed, superactive, mesic Aquic Hapludoll) and a Storden subsoil (fine-loamy, mixed, superactive, mesic Typic Eutrudept) with 18 Mg ha^-1 of three different "qualities" of bio-char along with 0, 56 112, or 224 kg ha^-1 of urea (46-0-0) to simulate N-enrichment. The field study used bio-char created with 10% atmospheric air present. Bio-char was applied at 0, 4.5 and 18 Mg ha^-1 along with 0, 56, 112, and 224 kg ha^-1 urea. Soil samples (0-30 cm) were taken to measure NH₄⁺-N and NO₃^--N concentrations weekly for the first eight weeks of the growing season in 2007 and post harvest. In 2008 heavy rainfall precluded collecting soil samples for the first three weeks of the growing season, but were started in week four and continued for five weeks and post harvest. Soil samples of 31-60 cm depth were also taken post harvest. Bio-char did not appear to affect NH₄⁺-N and NO₃^--N in either experiment. The properties studied tended to increase with increasing N-rates and the increases tended to have statistically significant differences due to N-rates.</p>