Incorporation of biochar into agricultural soils has been proposed as a potential best management practice (BMP) to increase crop yield and sequester atmospheric carbon (C). Furthermore, the production of biochar, referred to as pyrolysis, yields biofuel that can offset fossil fuels. Current research involving biochar and soil is mainly limited to greenhouse experiments and a few short-term field scale experiments. Here, biochar was incorporated into a field-scale corn (Zea mays)/soybean (Glycine max) system for analysis of soil mechanical and hydrological properties correlated with crop yield. A randomized complete block design was implemented with three biochar application rates: 0 Mg ha-1 (TC), 5 Mg ha-1 (TB5), and 25 Mg ha-1 (TB25). All plots were tilled using a tractor and rotovator in order to attain uniform incorporation of biochar. A small adjacent field was managed with no-till practices (NTC) to quantify the effects of tillage.
Biochar is an effective soil conditioner, evident by TB25 soil bulk density 9% and 18.5% less than that of TC and NTC, respectively. Analysis of soil pore size distribution resulted in TB25 with significantly increased macro-pores (1500 µm) related to water transmission and micro-pores (0.5 µm) related to water retention. Furthermore, plant available water capacity (AWC) of TB25 significantly increased by 9.6% and 29% over TC and NTC, respectively. Biochar amendment (TB25) increased saturated hydraulic conductivity (Ks) by 33% and 78% over TC and NTC, respectively. Soybean above-ground biomass and grain yield of TB25 resulted in respective 12.3% and 12.5% increases over TC. Correlation and linear regression analysis revealed significant positive trends with AWC, soil bulk density, total porosity, among other properties. Results suggest biochar is an effective soil amendment for temperate agricultural soils, yet long-term research will provide additional insight into the potential for biochar to improve soil quality, sequester atmospheric carbon, and enhance crop yield.