1a.Objectives (from AD-416):
The project objectives are to (1) compare the biomass performance across the Farm of four life-form plantings of several hundred acres made between 2008-2010 (all warm season grasses; warm season grasses and forbs; cool- and warm-season grasses and forbs; switchgrass monocultures); (2) compare the performance of switchgrass vs. diverse mixtures for biomass production and delivery of ecosystem goods and services across environmental gradients; and (3) conduct co-existence studies using transplants of switchgrass in different combinations with transplants of other native grasses and native legumes to determine the effect of varying plot composition on biomass production across environmental gradients.
1b.Approach (from AD-416):
Species native to the tall grass prairie region and available commercially will be screened based on structural and physiological characteristics that are likely to complement, not compete with, switchgrass. Plantings of these species and sampling of existing swards will be conducted along heterogeneous topographic moisture gradients (from dry hilltops to sub-irrigated lowlands) at the Prairie Farm, a 650 acre row crop farm located 25 miles south of Brookings, South Dakota, undergoing complete conversion to native prairie monocultures and communities. Experimental design will be quadrat sampling at equally spaced intervals within replicated transects along major environmental gradients. Enterprise budgets will be constructed for each of the life-form plantings based on the field operations and inputs used with each treatment. Biomass yields from switchgrass and mixes across environmental transects will be used with enterprise budgets to evaluate profitability of biomass production as a function of landscape for a range of biomass prices, and will be used to optimize profitability and provision of ecosystem services across the farm. The economic analysis will also calculate breakeven biomass prices at the farm level and across the farm landscape relative to the returns generated by typical corn-soybean production systems. Cradle to farm-gate life-cycle analysis (LCA) will be conducted based on energy and greenhouse gas (GHG) emissions associated with input use and estimated impacts of biomass production alternatives on soil carbon and trace gas emissions. The LCA will utilize the GREET model factors for energy and GHG emissions associated with agricultural inputs.
Field operations and input use data were collected for the establishment of life-form plantings. These data will be used to construct enterprise budgets and in conducting breakeven price analysis. These data will also be used in calculating the energy use and greenhouse gas emissions for the life-cycle assessment.