Biochar Mediated Changes in Soil Quality and Nutrient Uptake By Maize Crop in a Two Year Field Trial.

Biochar, a co-product of thermochemical conversion of lignocellulosic materials may be used as a soil amendment to enhance the sustainability of biomass harvesting.  Small plot experiment was established to test the effect of biochar on soil physico-chemical properties, nutrient uptake and yield of maize on Midwestern agricultural soil. Eighteen small field plots (23.7 m²) were established in Fall of 2010 by applying 0 to 112 Mg ha^-1 of hardwood biochar and incorporating it to a depth of 30 cm. Maize residue (6.5 Mg ha^-1) from the previous year’s crop was incorporated with the biochar and an additional 22.6 Mg ha^-1 of maize residue was spread on the soil surface in November to prevent soil erosion. During the 2011 growing season, the plots received a total of 377 kg ha^-1 of N fertilizer to minimize the risk of N immobilization. Biochar application had significant positive effect on grain yields, which ranged from 64 to 99% (6.9 to 10.7 Mg ha^-1) in the first year after application. We hypothesize that biochar applications mitigated the allopathic inhibition of plant growth induced by addition of 29.1 Mg ha^-1 of maize residue. A week quadratic relationship (P=0.15) between biochar and maize yield was observed in the second year; with, plots amended with 22 and 45 Mg ha^-1 of biochar having  the greatest yields.  Yield differences in second year were explained by the differences in plant available water content; plots amended with 22 and 45 Mg ha^-1 biochar had highest plant available water of 0.32 and 0.27 g cm^-3, respectively, compared to 0.24 and 0.21 g cm^-3 of control and 112 Mg ha^-1 biochar amended plots, respectively.  Biochar application significantly increased soil pH and decreased bulk density, but had no effect on CEC two years after application. The results indicate that biochar amendments have the potential to affect the fertility status and moisture characteristics of Midwestern agricultural soils.