Perennial Grass Covers Affect Long-Term Soil Quality

Perennial Grass Covers Affect Long-Term Soil Quality

Summary

This project seeks to compare different aspects of soil quality beneath cool- and warm-season grasslands in central Iowa, U.S.A. The proposed work is a direct outgrowth of our ongoing research at Bear Creek National Restoration Demonstration Watershed, and paves the way for continued, long-term research. Our goal in this project is to evaluate the long-term effects of two contrasting perennial cover-types, cool- and warm- season grasses, on soil carbon cycling, soil carbon storage, and soil food webs. This information is essential to the design of improved riparian buffers and Conservation Reserve Program planting in the Midwest and Great Plains regions.

Objectives:
1) To determine if cool-season and warm-season grasses differ in their soil organic carbon sequestration potentials;
2) To compare the soil food webs present beneath cool- and warm-season grasses;
3) To compare overall soil quality, as quantified by total respiration rate, in cool- ans warm-season grasses;
4) To develop best management practices for perennial cropping systems in reserved lands, filter strips, and riparian buffers.

Soil organic matter accumulation will be addressed by directly comparing total soil organic matter (SOM) contents of replicated cool- and warm-season grasslands, and along an age-gradient of established warm season grass buffers ranging from 1 to 11 years old. We expect that SOM pools will increase with site age in planted grasslands, and will be greater over the long-term in warm season grasslands. In addition, this information will provide baseline data for repeated measurements over 5-10 years intervals, allowing us to directly estimate soil C sequestration rates over the long term.

Soil food webs will be determined by sampling our replicated cool- and warm-season grass plots four times annually. Composited surface-soil samples from each plot will be sent to Soil Food Web, Inc., a private firm, for analysis of total and active fungal and bacterial biomass, nematode abundance and species composition, protozoan community structure, and soil macroarthopods. We expect that the cool-season grasslands will have higher microbial grazer populations than do warm-season grasslands, indicating functionally different soil ecosystems, and that differences observed will correlate with overall soil respiration rates.

Total soil biological activity will be assed in both cool- and warm-season grasslands throughout the snow-free season via measurements of soil carbon dioxide emissions. A key long-term objective of our research is the development of complete and accurate carbon budgets for cool- and warm-season grasslands, and this work is fundamental to that long-term effort.

Development of best management practices is an overarching goal of all of our on-site research, and a key objective of this study. We are particularly interested in determining the optimal species composition of planted grasslands, which we expect to vary depending on site and landowners objectives.

Collaborators: