Jumpstart of Soil Organic Matter by Biosolids/Compost Towards Climate-Smart Agriculture : Benefits to Soil Health, Carbon Sequestration, and Crop Yield

Rebuilding soil organic matter (SOM) to regionally specific targets for high quality soil that are likely maintained in the long term, here defined as “SOM JumpStart”, can unlock soil’s potential for increased productivity, enhanced resilience and reduced emission as the main components for climate-smart agriculture (CSA). A field experiment was established in 2013 at Fulton County, western Illinois to use highly stabilized organic amendment (HSOA) at a rate, potentially raising surface SOM of cultivated Alfisol (low quality soil) to the level of cultivated Mollisol (high quality soil for US Midwest). Treatments included one-time application of lagoon-aged air-dried biosolids at 165 Mg ha-1, one-time application of vegetative compost at 165 Mg ha-1, chemical fertilizer at 225-50-85 kg ha-1 yr-1 (N-P-K) as control, and grass fallow as reference. In every year following the HSOA application, fertilizer (N and K) rate was reduced by 25%, and no P was applied for most years. Corn was planted annually. The HSOA JumpStart application dramatically increased SOM, leading to soil organic carbon (SOC) at 2-2.5% after biosolids and about 3% after compost for 2013-2019, as that of Mollisol, while that in chemical fertilizer control remained unchanged at 1-1.2%. For the first seven years, HSOA JumpStart increased corn grain yield by a mean of 19.8% (biosolids) and 7.1% (compost) above the control, with greater increase at precipitations-abnormal (low/high) years. The SOM JumpStart caused the shift of soil microbial physiology to high C utilization efficiency, as evident by reduced microbial metabolic quotient for CO2, leading to the decrease in CO2 emission from agricultural crop residues by 19.6% (biosolids) and 20.0% (compost). Our modeling revealed the promising soil C sequestration (excluding residual C from HSOA) over next 50 years at 10.6 Mg C ha-1 by biosolids application and 13.9 Mg C ha-1 by compost application, higher than 6.8 Mg C ha-1 anticipated by “4 per 1000” international initiative. Even 50 years later, total SOC stock in JumpStarted soil is expected to be over 50% higher than that in control. Our results suggest the SOM JumpStart by HSOA such as biosolids and compost can transform conventional corn production to CSA