1a.Objectives (from AD-416):
To provide biomass suppliers with accurate guidelines for management of biomass removal and maintenance of soil quality.
1b.Approach (from AD-416):
Develop regionally applicable biomass feedstock harvest guidelines based on empirical and model analysis utilizing and enhancing available models; validate guidelines and recommendations through on-farm research trials; conduct regional sustainable biomass harvest round-table sessions with producers; characterize biomass feedstock and ash; assess impact of ash on plant growth and soil properties.
The overall goal of this project is to develop the data and tools necessary to assess long-term agronomic sustainability of removing corn stover residue for energy production, and is directly related to Objective 1 of the parent project: determine crop residue needs to protect soil resources and identify management strategies that enable sustainable production of food, feed, and biofuel and Objective 2: develop options for managing crop systems to reduce GHG emissions and increase C storage. The third set of on-farm plant samples were collected in the fall of 2011. Corn stover is predicted to be a significant bioenergy feedstock within the Upper Midwest. This subordinate project contributes to on-going research within the "Advancing Sustainable and Resilient Cropping Systems for the Short Growing Seasons and Cold, Wet Soils of the Upper Midwest" project, which is seeking to answer the question "How much biomass can be sustainably harvested from a given field and still maintain soil productivity?" Three plot-scale on-farm trials in corn-based rotations (corn-soybean on clay loam; corn-soybean-wheat on clay loam and corn-edible bean sandy loam soils) were established in west central MN to augment existing plots located at the Swan Lake Research Farm. Baseline soil properties were determined prior to harvesting any crop residue on each field. Crop yield was monitored annually following one-pass cob or stover harvest operation. Aggregate size distribution was measured by rotary sieve as an indicator of resilience to erosion. Two stover harvests from a corn-soybean rotation on clay-loam soil altered aggregate size distribution, indicating the aggregates were becoming less stable and more susceptible to erosive forces (wind and rain). One cycle of stover or cob harvest had little or no impact on corn, soybean, edible bean or wheat yield in on-farm trials. Likewise, three cycles of harvesting corn stover at the experimental site with a corn-soybean rotation did not substantially impact yield. However, after three-harvest cycles, aggregate size distribution shifted toward smaller aggregates that are less resilient to erosion at the expense of larger aggregates. Preliminary evidence suggests that the concentration of phosphorus and copper declined in the subsequent crop when stover is harvested. Results suggest short-term resilience of productivity does not predict long-term sustainability. In collaboration with university partners, we conducted two greenhouse experiments designed to evaluate phosphorus availability in potted soils amended with biomass ash corresponding soil incubations. Briefly, three soil types amended with four rates of combustion ash, gasification ash, pyrolysis char materials or inorganic phosphorus were incubated for 45 days. Greenhouse gas emission and nitrogen mineralization were monitored. Nitrous oxide emission was either not impacted or was suppressed by the application of amendment. However, divergent results were observed among soils. These experiments are being repeated to confirm results. This project also includes a modeling component. Integration of modeled and empirical data predicted that tilling with a moldboard plow or a chisel plow, even returning all crop residues to the field, was not enough to maintain soil organic matter.