Natalia Rogovska

A model for mechanistic and system assessments of biochar effects on soils and crops and trade‐offs

We developed a biochar model within the Agricultural Production Systems sIMulator (APSIM) software that integrates biochar knowledge and enables simulation of biochar effects within cropping systems. The model has algorithms that mechanistically connect biochar to soil organic carbon (SOC), soil water, bulk density (BD), pH, cation exchange capacity, and organic and mineral nitrogen. Soil moisture (SW)–temperature–nitrogen limitations on the rate of biochar decomposition were included as well as biochar‐induced priming effect on SOC mineralization. The model has 10 parameters that capture the diversity of biochar types, 15 parameters that address biochar‐soil interactions and 4 constants. The range of values and their sensitivity is reported. The biochar model was connected to APSIMs maize and wheat crop models to investigate long‐term (30 years) biochar effects on US maize and Australia wheat in various soils. Results from this sensitivity analysis showed that the effect of biochar was the largest in a sandy soil (Australian wheat) and the smallest in clay loam soil (US maize). On average across cropping systems and soils the order of sensitivity and the magnitude of the response of biochar to various soil‐plant processes was (from high to low): SOC (11% to 86%) > N2O emissions (−10% to 43%43%) > plant available water content (0.6% to 12.9%) > BD (−6.5% to −1.7%) > pH (−0.8% to 6.3%) > net N mineralization (−19% to 10%) > CO2 emissions (−2.0% to 4.3%) > water filled pore space (−3.7% to 3.4%) > grain yield (−3.3% to 1.8%) > biomass (−1.6% to 1.4%). Our analysis showed that biochar has a larger impact on environmental outcomes rather than agricultural production. The mechanistic model has the potential to optimize biochar application strategies to enhance environmental and agronomic outcomes but more work is needed to fill knowledge gaps identified in this work.

Biochar effect on severity of soybean root disease caused by Fusarium virguliforme

Background and aimsBiochar is known to decrease soil bulk density, increase nutrient and water retention, and to suppress certain soil-borne pathogens. The aims of our glasshouse and field experiments were to; 1) determine whether biochar amendments impact the severity of soybean root rot caused by Fusarium virguliforme; 2) to determine if biochar reduces severity of root rot by changes in physicochemical properties of soil; 3) whether biochar induces systemic resistance to root rot in soybean plants.ResultsResults of the first glasshouse pot study indicate that biochars differ significantly in their effect on root rot caused by F. virguliforme, as two of eight biochars significantly suppressed root rot severity. Results for the second glasshouse pot study indicate that disease suppression was not related to changes in soil physicochemical properties (bulk density, soil moisture, soil pH). A third split-root experiment provided no evidence that biochar amendments are capable of inducing systemic resistance in soybean plants. Results of the small plot experiment proved that biochar was effective at reducing visual above ground symptoms of SDS, but did not affect soybean grain yields.ConclusionsBoth systemic and indirect effects of biochar on SDS root rot severity have been eliminated in the present study; further research is needed to determine whether suppression of root rot severity is related to changes in soil microbial communities induced by biochar.