Biochar Age and Crop Rotation Impacts on Soil Quality

Abstract

Core Ideas Crop rotations including switchgrass were found to build soil organic C and N Biochar amendments increased soil C and N, pH, and gravity drained water content Total soil C and N increases with biochar age suggest negative priming Biochar and switchgrass offset negative effects of biomass harvesting on soil quality Corn residue removed from Midwestern farms is a large potential source of biomass for cellulosic bioenergy production in the US long‐term harvesting of biomass, however, may lead to the degradation of soil quality unless management practices that compensate for the removal of biomass are used. In this study, biochar amendments and long‐term crop rotations that include triticale and switchgrass with corn and soybeans were hypothesized to reduce the negative effects of biomass harvesting on soil quality. Chemical breakthrough curves, measured for intact soil cores indicate that crop rotations that include switchgrass or triticale increased both retardation and dispersivity relative to conventional rotations and biochar amendments decreased dispersivity relative to controls. Across all crop rotations, there was an increase in total soil C and N, soil C/N ratio, pH and gravity drained water content, and a decrease in bulk density for soils treated with biochar relative to no‐biochar controls. No significant effect of biochar age on soil physical properties was measured in 2014 but significant increases with biochar age were found for total soil C and N in 2016, suggesting a synergistic interaction (negative priming). Continuous switchgrass stands were found to build soil organic C and N, increase retention of plant available P and K, and lower bulk density relative to the continuous corn cropping system. The results suggested that soil biochar amendments and crop rotations that included switchgrass helped mitigate some of the adverse effects of biomass harvesting on soil quality.

Soil carbon increased by twice the amount of biochar carbon applied after 6 years: Field evidence of negative priming

“…Effects could develop in the longer term (>6 years) as biochar ages and reacts with other soil constituents. For example, old wood biochar can absorb more water or repel less water than fresh wood biochar (Aller et al, ; Briggs, Breiner, & Graham, ), which suggests that water retention capacity of soil–biochar mixtures may increase with time after application. The soils at our study site were silty clay loams, which may be slower to respond to biochar application due to the high clay content relative to coarse‐textured soils. Previous studies suggested that sandy soils are more responsive to biochar application than fine‐textured soils (Blanco‐Canqui, ).…”

Long term biochar effects on corn yield, soil quality and profitability in the US Midwest

“…The wide range of options for residue management and the complexity, uncertainty, and long 70 time-scales underpinning the outcome of these options makes it difficult to develop sound 71 residue management strategies for optimizing the agronomic and environmental benefits based records and periodic soil organic carbon data were available (for details see Aller et al, 2017).…”

Drought stress and Acacia seyal biochar effects on sorghum gas exchange and yield: A greenhouse experiment

“…It may be that the ecophysiological effects of biochar on crops grown under drought stress require high doses and are limited to sandy soils, and only appear after the biochar has become fully integrated into the soil (Cornelissen et al, 2013;Mulcahy et al, 2013). More research is needed to explore whether biochar addition in field conditions can improve the water availability to crops in the longer term, as it could be expected that SOC contents would increase as a result of the negative priming effect of biochar on the mineralization of soil organic matter (Aller et al, 2017;Madari et al, 2017).…”

“…In recent years, the use of biochar has been promoted as a soil amendment especially in tropics because of its ability to retain nutrients in the soil and to improve soil water holding capacity (Omondi et al, 2016;Aller et al, 2017;Jeffery et al, 2017). Biochar has been reported to also improve some ecophysiological traits and yields of plants grown under drought stress (Major et al, 2010;Mulcahy et al, 2013), even when the amount of available water would be unaffected by biochar (Kammann et al, 2011).…”