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

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

Summary

There were no differences in shoot biomass yield related to pasture type (silvo vs. open) or treatment (N fertilizer vs. clover) at the Americus site. However, shoot biomass yield was 50% higher (P<0.05) in May vs. June or August in both silvo- and open-pastures. Biomass yield varied spatially at all sampling dates: 21, 23 and 16% reductions (P<0.05) between the lane ‘middle’-‘mid-center’ average were measured at the ‘side’ position in May, June and August, respectively. Under- and over-story cover composition measurements in May 2006 detected a significant (P<0.05) 9% increase in pine-cover over the portion of the lane closest to the tree sets; that increase is likely contributing to the significant decrease in forage biomass at the ‘side’ position. As in 2005, there were no spatial differences detected in %WSA between May and August and %WSA was significantly (P<0.05) higher in August. However, unlike 2005, this %WSA increase was only 8% versus the 23% temporal increase noted in 2005. Another difference from 2005 was that in both May and August, the %WSA levels in the clover-treated soils were significantly (P<0.05) higher than in the fertilizer-treated soils; these increases were 5% in May and 14% in August. This increase was noted even though a stand of crimson clover did not result from seeding of the previous crop. Overall, there was an 11% decrease in FHD between May and August. However, this decrease was significantly higher in open (-20%) vs. silvo- (-3%) pasture soils.
Prior to initiating the grazing phase of the study at FVSU, the plant species were identified and quantity recorded along random transects. The relative quantity of each species was recorded as either understory material or as overstory material. A total of 38 plant species were identified in the understory. Fecal samples were stored according to standard laboratory procedures, and were then later used to identify plant species consumed at various points as each paddock was eaten down. The outcome will provide detailed information on plant species preferences for the goats. Preliminary data from the first year of this component suggested that the goats refused to eat only sickle pod, spleenwort, and nightshade.
Grazing management procedures were such that when all vegetation was removed from each paddock, the animals were moved off the experiment site until such time as such regrowth had occurred to justify restocking. Because of the relatively late start in the grazing cycle in 2006, the animals were returned only one time before frost and cool weather put a stop to plant regeneration and growth.
Lessons learned and observations during the 2006 grazing season.
Goats will eat nearly all vegetation on offer in a wooded area of land, but there must be sufficient open sky to allow vegetation to grow and regenerate.
Collecting fecal samples is not a difficult process as long as samples are collected relatively fresh. The early morning hours seem best, as the animals were rising.
Goats can be contained with portable electrified plastic netting so long as training has taken place in advance and so long as there is a critical number of animals in any particular group. We have not yet determined what that number may be.
An obvious change in the “openness” of the experimental area was evident following grazing during this first year.
Random monitoring of the does suggested that internal parasite burden was light, based on fecal egg count.
Some animal weight loss did occur during the course of the grazing period since the experimental plan required that animals be forced to consume all plants they possibly could. Less intensive grazing would result in less defoliation.
Objective #4 – Examine the economic feasibility and level of landowner acceptance of management practices being proposed.
Two field days, held at the Owens and Evans Farms were attended by over 100 landowners, foresters, natural resources professionals, and extension and university personnel. This attendance represented approximately 9,000 managed acres in the coastal plain. Fifty percent of the participants responded that that they had learned something new at the field day and wanted additional information about silvopasture.
It is too early in the FVSU study to begin compiling feasibility data and landowner acceptance of the practices. At the end when all experiment data have been reviewed, then the economic components will be added. A field day planned for 2007 will provide some measure of landowner acceptance to the use of goat (or sheep) in vegetation management.
Objectives 5 – Analyisi of weather data and hydrologic site characteristics is underway.

Objectives/Performance Targets

Objectives

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).

Accomplishments/Milestones

Objectives 1 and 2
At Americus GA, pastures were sampled for fertilization requirements in January. Fertilizer was applied according to soil test recommendations in May. In the ‘clover’ treatments, the stand of crimson clover planted in fall 2004 which was allowed to reseed in spring 2005 did not result in a successful clover stand for spring 2006; drought conditions were considered the likely cause. Even without a successful clover stand, no fertilizer N was added to the ‘clover’ treatment plots. ‘Dixie’ crimson clover was replanted in fall 2006. Since a reduction in forage biomass within the lane between double-row tree sets had been detected at sampling points closest to the sets in August 2005, an additional biomass sampling point (‘mid-center’) was included equidistant between the ‘side’ (1 m from the center of the tree base) and ‘middle’ (equidistant in the lane between the double-row sets) lane positions. Biomass in open pastures was sampled as in 2005. In both silvo- and open-pastures, shoot biomass was clipped above 5 cm from 0.25-m2 quadrats. Soil samples were collected to characterize % water stable aggregates (%WSA) and fungal hyphal density (FHD, g/m dry wt) in May then again in early August at the side and middle lane positions in silvopasture paddocks and in a similar configuration in open-pastures. There were no differences in shoot biomass yield related to pasture type (silvo vs. open) or treatment (N fertilizer vs. clover). However, shoot biomass yield was 50% higher (P<0.05) in May vs. June or August in both silvo- and open-pastures. Biomass yield varied spatially at all sampling dates: 21, 23 and 16% reductions (P<0.05) between the lane ‘middle’-‘mid-center’ average were measured at the ‘side’ position in May, June and August, respectively. Under- and over-story cover composition measurements in May 2006 detected a significant (P<0.05) 9% increase in pine-cover over the portion of the lane closest to the tree sets; that increase is likely contributing to the significant decrease in forage biomass at the ‘side’ position. As in 2005, there were no spatial differences detected in %WSA between May and August and %WSA was significantly (P<0.05) higher in August. However, unlike 2005, this %WSA increase was only 8% versus the 23% temporal increase noted in 2005. Another difference from 2005 was that in both May and August, the %WSA levels in the clover-treated soils were significantly (P<0.05) higher than in the fertilizer-treated soils; these increases were 5% in May and 14% in August. This increase was noted even though a stand of crimson clover did not result from seeding of the previous crop. Overall, there was an 11% decrease in FHD between May and August. However, this decrease was significantly higher in open (-20%) vs. silvo- (-3%) pasture soils.
Even though drought conditions affected the study site, between 5 and 7 days of grazing for 5-6 animal units were available in June and August, respectively on both silvo- and open-padture sites.
Greenhouse studies were completed in 2006 to study the influence of forage species and soil pH level on water stable soil aggregates under protected culture. These studies suggest that both soil pH and forage species have significant impacts on the percent water stable aggregates in pasture soils.
Objective #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.
At the Fort Valley State University (FVSU) site, a total of 45 mature Spanish does were allocated to three stock rates. Prior to allocating to treatment each does was weighed and those weight data were used to create more uniform groups and total weight. Grazing began on July 27 after a period of conditioning to electric fencing in the form of electro-netting.
A total of 12, 0.8-acre paddocks were available for grazing. The paddocks were stratified according to canopy so that there were six levels of canopy. Two paddocks where were extremely open or extremely covered (very little grazing material under the trees) were excluded from the grazing paddocks. The remaining ten paddocks were allocated to that there were two allocated for no treatment, treatment with herbicide, or one of the three stocking densities.
The equivalent stocking rates were 12.5 animals per acre, 19 animals per acre, and 25 animals per acre. Grazing in any single paddock continued until ocular scores suggested that all edible material was removed. The number of days to reach the level of no edible material varied with stock density.
Prior to initiating the grazing phase of the study, the plant species were identified and quantity recorded along random transects. The relative quantity of each species was recorded as either understory material or as overstory material. A total of 38 plant species were identified in the understory. There was an abundance of diversity although five species made up the majority. In addition some areas of bare ground and leaf litter were identified. The overstory was composed of 11 species. Open sky was occasionally seen where there was no overstory at the sample site.
Fecal samples were collected from dung piles from a number of random animals within each animal group. The number of animals sampled varied with stocking rate.
Fecal samples were stored according to standard laboratory procedures, and were then later used to identify plant species consumed at various points as each paddock was eaten down. The outcome will provide detail information on plant species preferences for the goats. Preliminary data from the first year of this component suggested that the goats refused to eat only sickle pod, spleenwort, and nightshade.
Grazing management procedures were such that when all vegetation was removed from each paddock, the animals were moved off the experiment site until such time as such regrowth had occurred to justify restocking. Because of the relatively late start in the grazing cycle in 2006, the animals were returned only one time before frost and cool weather put a stop to plant regeneration and growth.
Lessons learned and observations during the 2006 grazing season.
Goats will eat nearly all vegetation on offer in a wooded area of land, but there must be sufficient open sky to allow vegetation to grow and regenerate.
Collecting fecal samples is not a difficult process as long as samples are collected relatively fresh. The early morning hours seem best, as the animals were rising.
Goats can be contained with portable electrified plastic netting so long as training has taken place in advance and so long as there is a critical number of animals in any particular group. We have not yet determined what that number may be.
An obvious change in the “openness” of the experimental area was evident following grazing during this first year.
Random monitoring of the does suggested that internal parasite burden was light, based on fecal egg count.
Some animal weight loss did occur during the course of the grazing period since the experimental plan required that animals be forced to consume all plants they possibly could. Less intensive grazing would result in less defoliation.
Objective #4 – Examine the economic feasibility and level of landowner acceptance of management practices being proposed.
Two field days, held at the Owens and Evans Farms were attended by over 100 landowners, foresters, natural resources professionals, and extension and university personnel. This attendance represented approximately 9,000 managed acres in the coastal plain. Fifty percent of the participants responded that that they had learned something new at the field day and wanted additional information about silvopasture.
It is too early in the FVSU study to begin compiling feasibility data and landowner acceptance of the practices. At the end when all experiment data have been reviewed, then the economic components will be added. A field day planned for 2007 will provide some measure of landowner acceptance to the use of goat (or sheep) in vegetation management.
Objectives 5 – Analyisi of weather data and hydrologic site characteristics is underway.

Impacts and Contributions/Outcomes

The second year of data was collected at the Americus site. This will continue in 2007 with the addition of observations of cattle behavior in silvopasture versus open pasture at the Owens Farm beginning in March 2007.
Data on the microhistological composition and quality of goat diets will be continued at the Fort Valley site in 2007.
In addition to successful field days at the Owens and Evans Farms in 2006 and a technical field day at the Americu site, additional field days are planned for the Owens Farm in April 2007, the FVSU site in June 2007 , and the Solon-Dixon Center in Andalusia AL in September 2007.
A paper will be presented on the Americus data at the 10th International Agroforestry Conference in Quebec City in June 2007.
Though evaluation of management strategies designed to maitain forh pasture productivity and soil quality, results from thsi 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 options.

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