Understanding Plant-Soil-Livestock Interactions: A Key to Enhanced Sustainability in Southern-Pine Silvopasture Systems

2005 Annual Report for LS05-174

Project Type: Research and Education
Funds awarded in 2005: $120,000.00
Projected End Date: 12/31/2008
Region: Southern
State: Alabama
Principal Investigator:
Mary Goodman
Auburn University

Understanding Plant-Soil-Livestock Interactions: A Key to Enhanced Sustainability in Southern-Pine Silvopasture Systems


In May, species composition measurements at Americus determined that canopy cover of crimson clover was approximately 15% in both bahiagrass (Paspalum dilitatum) silvopasture and open-pastures. There were no shoot biomass yield differences as a result of spatial comparisons (1 m from tree centers in lane vs lane middle) in May however, clover-treatments had a significantly higher biomass yield by 28% in clover- versus comparable N-fertilizer treatment paddocks. No differences in shoot biomass yield were detected in July however, in the silvopastures in August, there was a significant 10% reduction in biomass yield at sampling points closest to the trees versus the lane middles. No treatment or spatial differences were found in percent water-stable aggregates (%WSA) however, there was a significant temporal difference as %WSA increased overall by 23% in August versus June. Soil strength (J/m2) increased with depth however, sample sites closest to the trees showed a 50, 56 and 43% reduction in soil strength at 5, 10 and 15 cm, respectively. When 17 individual forage species were compared to a no-plant control in soil from the Americus site under greenhouse conditions, 3 of the forages had a significantly positive effect on percent water-stable soil aggregates while 4 of the forages significantly reduced percent water-stable soil aggregates.

Objectives/Performance Targets


1. Determine the impacts of N supply (fertilization versus clover) on above- and below-ground forage productivity, forage quality and plant diversity in developing silvopasture.
2. Determine the impacts of N supply on pasture soil structural stability and relationships to soil compaction, and water infiltration and retention in developing and mature silvopasture.
3. Compare the use of small ruminants to the more conventional use of herbicides to control invasive broadleaf plants within developing silvopasture systems and impacts on infiltration.
4. Examine the economic feasibility and level of landowner acceptance of management practices being proposed.
5. Estimate effects of silvopasture management practices on watershed-level hydrology using the Hydrology Simulation Program-Fortran (HSPF).


At Americus, a successful stand of ‘Dixie’ crimson clover (Trifolium incarnatum) was obtained from the October 2004 planting; clover was sown at Andalusia in October 2005. Pastures at Americus, Andalusia, and Chipley had been sampled in March for fertilization requirements. Fertilizer was applied according to soil test recommendations in May; no fertilizer N was added to the clover treatment plots. Soil samples were collected at full clover bloom in May and again in early August at two points on 5 separate transects positioned perpendicular to the tree strips in each silvopasture and in a similar configuration in the open-pasture paddocks at Americus. On each transect, one sample site was located 1 m from the center of the tree base and the other at the midpoint between adjacent sets of tree strips. In May and August, the samples were analyzed to characterize percent water-stable aggregates (aggregate stability); soil compaction was measured in situ at 5-cm increments to 20 cm in July. In August, 15-cm soil cores were collected to characterize root biomass. Shoot biomass above 5 cm was clipped from 10 0.25-m2 quadrats in each paddock along transects at points used for soil sampling in May, July and August. All paddocks at Americus were fenced and water installed in June 2005. In September, vegetation was characterized at 6000 points each for understory and overstory at the woodlot set for use at the Fort Valley site. The Fort Valley site will be fenced in late April 2006 and water installed; grazing with goats will begin in May 2006. Portable weather stations were assembled and located in silvopasture and open pasture at Americus (5-yr old Pinus palustrus)and Chipley FL (20-yr old Pinus taeda)and launched in early November 2005. The first greenhouse study was greenhouse study was planted August 12 and completed December 22, 2005. The second greenhouse study will be planted in August 2006. Soil compaction and percent water-stable aggregates were chatracterized in silvopasture sites at Fort Valley in September, Chipley in November and at Andalusia in December.
In June 2005, producer field days were planned for spring and summer 2006: Owens Farm, Chipley FL April 5, 2006; Evans Farm, Jakin GA June 15, 2006; JCPMC, Americus GA July 27. Additional producer field days will be planned in June 2006 for Solon Dixon Forestry Education Center, Andalusia AL and Fort Valley State University in Fall 2006. An MS animal science student was recruited for the project in March 2006 and will begin Summer Semester 2006. Planning for 4 producer training sessions to be held in 2007 will begin in June 2006. Preliminary results for the hydrologic modeling will be completed in June 2006.

Impacts and Contributions/Outcomes

Through evaluation of management strategies designed to maintain both pasture productivity and soil health (quality), results from this project will provide understanding that will allow Southern Region producers to move more profitably toward conversion of perennial pastures to silvopasture and sustainable long-term use for several ruminant livestock production options.


Michael Hall

GLCI Specialist
East National Technology Support Center
200 East Northwood Street, Suite 410
Greensboro, NC 27401
Office Phone: 3363703361
Will Getz

Associate Professor, Animal and Food Science
Fort Valley State University
College of Agriculture, Home Economics, and Allied
PO Box 4061
Fort Valley, GA 31030
Office Phone: 4788256955
George Owens

Owens Farm
Chipley, FL 32428
Office Phone: 8506381733
Andy Andreasen

County Extension Director IV
University of Florida
1424 Jackson Avenue, Suite A
Chipley, FL 32428-1628
Office Phone: 8506386180
Rick Hatten

Georgia Forestry Commission
PO Box 819
Macon, GA 31202-0819
Office Phone: 4787513500
Darrell Rankins, Jr.

Extension Specialist and Associate Professor
Auburn University
Department of Animal Sciences
209 Upchurch Hall
Auburn University, AL 36849
Office Phone: 3348441546
Mack Evans

Evans Farm
2350 Masonic Road
Jakin, GA 39861
Office Phone: 2297932335
Malcome Kirkland

Agronomist/Assistant Manager
NRCS-Jimmy Carter Plant Materials Center
295 Morris Avenue
Americus, GA 31709
Office Phone: 2299244499
Marc Thomas

Outreach Coordinator
Georgia Forestry Commission
PO Box 819
Macon, GA 31202-0819
Office Phone: 4787513500
Susan Sladden

Research Associate
Auburn University
Department of Agronomy and Soils
202 Funchess Hall
Auburn University, AL 36849-5412
Office Phone: 3348443964
James Walter Prevatt

Extension Specialist and Professor, Ag Economics
Auburn University
Department of Agricultural Economics and Rural Soc
203 Comer Hall
Auburn University, AL 36849
Office Phone: 3348445608
Nathaniel Brown, Jr.

Professor, Resource Economics
Fort Valley State University
College of Agriculture, Home Economics and Allied
122A Tabor Building
Fort Valley, GA 31030-4313
Office Phone: 4788256812
William Kingery

Professor, Environmental Soil Science
Mississippi State Unviersity
Department of Plant and Soil Sciences
PO Box 9555
Mississippi State, MS 39762
Office Phone: 6623252748
Larry Stallings

Forestry Tech IV/Silvopasturalist
Auburn University
Solon Dixon Forestry Education Center
12130 Dixon Center Road
Andalusia, AL 36420
Office Phone: 3342227779