Biochar impact on Midwestern Mollisols and maize nutrient availability

• Biochar may mitigate adverse effects of allelochemicals from decomposing residue on maize yields.
• Biochar application decreased soil bulk density and increased surface volumetric water content.
• High rates of biochar did not adversely affect plant nutrition or corn grain yields.

Biochar applications have been shown to increase crop yields on acidic and low activity soils in the tropics but fewer positive yield responses have been reported for temperate soils. We hypothesized that even without a yield response, applying biochar to a Midwestern Mollisol could improve soil quality and plant nutrient availability because of the carbon it supplies and its conditioning effect. Eighteen small field plots (23.7 m2) on a glacial-till derived soil were established by incorporating 0 to 96 Mg ha− 1 of hardwood biochar to a depth of 30 cm. Several soil quality indicators, plant nutrient availability, uptake, and yield of two consecutive maize (Zea mays L.) crops were monitored. Biochar application significantly increased soil pH, readily available water (RAW) content (defined as volumetric water available between − 10 kPa and − 100 kPa) and soil organic C (SOC). It decreased bulk density (BD), but had no consistent effect on soil infiltration rates, CEC, or nutrient uptake. Biochar application did increase grain yield during the first year by 11 to 55% following very high stover application rates (3.5 × the typical amount), presumably because biochar mitigated adverse effects of allelochemicals released from the decomposing maize residue. There was no detectable biochar effect on maize yield during the second year when the crop was limited by severe drought.