During the past year, work has continued toward achieving the goals set forth in the original proposal. Work over the last year has included sample collection, chemical analyses, and data collation and analysis. In addition to the scheduled tasks, we have completed two manuscripts examining the implications of different sampling schemes on our ability to detect chnges in soil C over time, two manuscripts (in prep), and a presentation, on results from comparative soil sampling in virginia.
An initial reconnaisance visit to Tennessee and Kentucky took place in March, 2000. Gregg Brann (NRCS, Nashville) and I visited six demonstration farms. Of the farms there, three had land use/management contrasts that fell under the perview of this project. One of the farms had pastures that had been grazed differently (MiG vs. extenive), one had pasture, forest, and cultivated fields on the same soil type, and the other had rotataionally grazed/fertilized, extensively grazed/fertilized and extensively grazed/unfertilized pastures. All of these fields were sampled in June 2000.Locations of microsites were established with a differential GPS and a relocatable marker ball was installed at each microsite so that the exact locations of the soil cores can be revisited in the future. Soil cores comprising more than 1T of soil were returned to NREL and sample preparation and analysis began in December.
In addition to continuing to prepare and analyze samples for total soil C, we evaluated our sampling scheme against other sampling schemes using data from Virginia. Our results show that three mirocplots with six cores each is the most efficient of designs with 18 cores per field. Together with analysis of the broadest national soil C database available (NRCS Pedon database), these results were presented at a meeting in North Carolina in November 2000 (click here for slides) and were accepted for publication in a special issue of environmental pollution. Likwise, in addition to processing the samples from TN for soil C, we analyzed each soil core individually to evaluate the how well our sampling scheme can be used to detect small changes in soil C over time. For this portion of the project, the EPA funds were augmented by a grant from the Bradely Fund for the Environment. Results show that changes on the order of those likely to occur with changes in pasture management over five years can be detected with sampling schemes similar to the one we used.
| 1998 | 1998 | 1998 | 1999 | 1999 | 1999 | 1999 | 2000 | 2000 | 2000 | 2000 | 2001 | 2001 | 2001 | 2001 | 2002 | |
| Research task | Su | A | W | Sp | Su | A | W | Sp | Su | A | W | Sp | Su | A | W | Sp |
| Task 1 - Landuse/Recon. | VA | VA | VA/MS | VA/MS | TN/KY | |||||||||||
| Task 2 - Field comparisons | VA | MS | TN | |||||||||||||
| Task 3 - Soil Processing | VA | MS | MS | MS | MS | TN | TN | TN | MS | MS | MS | MS | TN | TN | ||
| Task 4 - Modeling | VA | VA | VA/MS | MS | MS/TN | TN |
Results from soil sampling in Virginia have been assembled into a manuscript in prep for Geoderma. Our results show that MiG lead to more soil C for all four of our paired farms (Fig. 1). Root C and litter C tended to decrease in response to MiG, but those changes were small relative to soil C; total system C increased with MiG. The largest (50%) poriton of total change occurred in the top 10cm (for 50cm total). We are in the process of writing a companion paper that evaluates the impacts of land use on soil C from data collected at Billy Wayson's farm. We anticipate that these manuscripts will be submitted by early fall.
We have completed many of the tasks scheduled for the third year of the project, though soil processing has been slower than anticipated. Further, or modeling work has been delayed due to problems incorporating MiG - which has weekly or daily management variability - into the Century model framework - which typically operates on a monthly timestep. We have been able to do some modeling work in support of Don Johnson's research - we modeled how changes in land use driven by changes in grazing management (e.g. less demand for feed corn) affect soil C. Presentations were given at the global sustainability conference in Illinois (slideshow, March, 2000) a carbon meeting in Iowa (poster at 'Carbon: Exploring the Benefits to Farmers and Society' July 2000), at the Ecological Society of America annual meeting (poster, August 2000), at a meeting in North Carolina (slideshow at Advances in Terrestrial Ecosystem Carbon Inventory, Measurements, and Monitoring, November 2000) and at the First National Grazing Conference in Las Vegas (slidewhow, December 2000). Over the coming year, we plan to complete sample processing for Mississippi and Tennessee, configure the Century model to reflect a wider variety of grazing management schemes, and continue to present and publish results.