Improving the Cost-Efficacy of Silvopasture Establishment in the Southeast

Results of Tree Establishment

• Due to wild bird consumption, Winter Rye was seeded twice. At this density, it had an allelopathic affect on trees. Exact seeding rate unknown due to amount lost to wild birds.
• Due to drought (and allelopathy), all tree species had difficulty establishing. Irrigation hose was installed along all plots, but only after the worst period of drought had passed. Apart from mulberry, no tree species were well-enough represented throughout all plots to measure accurately. Therefore, observations were made for the mulberry only. (Mulberry did not succumb to the drought, and is well-represented through all plots.)
• Because drought and cover crop allelopathy created such difficult growing conditions, in 2023, trees were watered several times, and fertilized once.
• Rye that was on lower quality soil grew less vigorously. Apparently due to this, overall tree growth on the poor soils was actually better than on the good soils, early in the trial. Later in the trial, good-soil plots had caught up.

Deterrent Establishment

• Due to drought during the first year of the project, deterrents had a difficult time establishing. The two herbaceous deterrent species (Wingstem and Mints) successfully established in all replications. The two woody species, however (Elderberry and Blackberry) established only erratically, and not consistently enough to provide accurate data between replications. Therefore, only the herbaceous deterrent species were observed.

Project Extension

• The project manager applied for and received a 12-month extension, to give more time for the trees and deterrent species to establish, before applying heavy timed grazing. However, informal observations were made during several grazing periods (described below).

Initial Results

• In the second and third years of the project, during informal grazing periods, the following was observed:
  • Initial tubes (5' Tree Pro Slit tube) with bamboo stakes were heavily damaged by wind, and had to be removed. They were replaced with 6' Plantra Sunflex systems, which did not succumb to any wind damage.
  • While the wind-dismantled Tree Pro tubes were pulled off and scattered by the cattle, no browsing damage occurred on the Plantra tubes.
  • All other plots were grazed, though not heavily. A two-strand polywire fence was set between the trees and the cattle, with lower strand at approximately 22” and upper strand at approximately 34”, charged and running at over 7 kv (exceeded tester capacity).
  • There was no apparent difference between the grazing that occurred on the plots with plant or brush deterrents, or the control. The only apparent difference was the lack of grazing on the trees in tubes (which cattle simply could not access).
  • Both plant deterrents and brush deterrents were relatively small in size or low to the ground, whereas Mulberry forage was thick and robust and tall. The deterrents simply were not at the correct scale to protect the trees from grazing.
• In the last year of the project, the project manager had a child, delaying the application of heavy timed grazing at pre-specified densities.
• As of Spring 2025, both herbaceous deterrents are growing vigorously, whereas the woody deterrents have all but disappeared, and the cut brush deterrents have disintegrated. All Mulberries are growing vigorously and up to 8’ tall. Tubes are still in place and trees have come out the top. Growth in the Control plots, tubes, and all deterrent plots is more or less the same, with Mulberries on the “good” soils roughly 1’ taller on average than those in the poor soils.

Future Plans for the Project

• In May of 2025, we plan to measure, then coppice all of the Mulberry to 4” off the ground. This will result in strong regrowth of many stems, at a lower height. In June, we plan to replace the disintegrated woody deterrents with freshly cut brush. In July, August, and September, we plan to apply heavy timed grazing at the two prespecified densities of 10k and 100k lbs/acre. After each grazing, we will measure the height and characterize the condition of each of the six remaining active plots (we will exclude the 2 plots originally planted with woody plant deterrents that did not establish successfully). We will compare the establishment success and grazing deterrence effectiveness for all treatments. We will submit that as an addendum to our project in late 2025.

Initial Conclusions

• Winter rye can have a disastrous effect on young tree seedlings. Since other cover crops are also known to have allelopathic affects as well, we recommend care in using these with young trees. Careful control of seeding rates and use of diverse mixes that do not overly rely on any one species, is advisable. Also, one should be prepared to invest in methods of protection for seed during establishment. We used ample straw, but the swarming birds at that time of year just picked through it. A livestock guardian dog fenced into the area, scarecrow or other visual deterrent, or woven fabric to lay over the seed while it was germinating might have helped.
• Moving woody plant deterrent species that rely on taproots, like Elderberry and Blackberry, is not effective. Fibrous-rooted woody species may be more successful. In the case of using taprooted species, planting into an established stand -- if physically feasible -- may prove more effective (more closely mimicking the process observed in the UK precendent cited in our background literature).
• Mulberry is a very vigorous grower that does not seem to mind drought or poor soils or heavy pruning. Persimmon and pine, however, were very susceptible to drought and poor soils. Hybrid poplar did not respond well to the drought, but several trees did come back (“sucker back”) with new growth, whereas the pine and persimmon trees mostly died out-right.
• We recommend beginning silvopasturists in our region start with Red Mulberry to gain their skills and develop routines for managing fodder banks. (We prefer using Red Mulberry rather than the invasive White Mulberry, which threatens the native Red Mulberry⁽¹⁾.) For areas with ample rainfall, drought should not require irrigation to keep Mulberry alive, due to its quick ability to drop leaves and remain leafless without dying. Mulberry is also very easy to cut and plant as livestakes, increasing the density or breadth of the fodder bank.
• For developing Mulberry fodder banks, we recommend planting densely and mulching heavily, then using two strands of polywire with a moderate electric charge, and no tubes or deterrents other than the fence. This will likely need weedeating and/or mowing the perimeter multiple times a year for the first year or two, even with fairly dense grazing.
• If using Mulberry, and receiving ample rainfall, after two to three years, trees will have grown several feet tall and weedeating and mowing requirements should reduce or cease. We anticipate at this time that the fence can be removed and the fodder banks grazed openly, without permanently damaging the trees. We plan to try this in 2026 after the trees have regained some height, and will report our findings. Currently, our Mulberry stems range from 1” to 3.5” in diameter, and we do not believe at this size that they would be threatened by cattle at any density, so long as they had ample time (2-3 months) to recover, as well as a final ungrazed growing session before the end of the year.
• For developing “standard” trees, with single upright boles, we do not at this point recommend using any method other than a high-quality tube. The plots with high-quality tubes with sturdy stakes were completely untouched by the cattle. (However, it should be noted that elsewhere on the farm, we use the same tubes with energized polywire wrapping the tube. It is possible that had this not been the case, animals would have shown curiosity in the tubes and removed or dismantled the tubes.) One benefit of the tube in this case was that it is easy to work around with a string-trimmer, as the tube withstands minor string-trimming and allows you to cut back vegetation between and around the trees very quickly compared to unprotected trees, or trees with living deterrents that must be carefully (slowly) avoided.
• Our search continues for a sourced-on-site, plastic-free, no-waste deterrent. We will continue to monitor these plots and observe the effectiveness over time as the herbaceous plant deterrents mature and multiply. Of the methods we tried, we have the following impressions:
  • Planting trees as 18”-3’ bareroot seedlings into an existing plot of herbaceous plant deterrents (a colony of wingstem, for instance) might result in better deterrence than planting the deterrent and the tree at the same time, because the deterrent would already be tall enough to shroud the tree. In this case, it would be important that only shade-tolerant tree species be used.
  • Planting trees as livestakes or seeds/nuts into an existing plot of woody vegetation might be successful (if difficult); this was described as a practice used in the UK in the project proposal (and every unmowed part of our fields grows up first in shrubs and later in trees).
  • One would be best off using cut brush as a deterrent in a scenario where
    1. There was already a very large amount of brush already going to be cut and disposed of;
    2. Brush pieces were arranged so that none that make good “back scratches” were available to the grazers;
    3. Planted tree species were relatively fast-growing; and
    4. Planted trees could be planted as seeds or livestakes AND/OR brush contained no thorns.
  • We found that the thorns were problematic to us as humans, but not so much so to the cattle. We think the general “unappealing look” of a brush pile to a bovine is the main reason they would avoid it. We also found it is important to be able to get into the pile, plant the tree rapidly, then extricate oneself – a process which works much more easily with livestakes and non-thorny species. Otherwise the planting is practically unfeasible.

⁽¹⁾ https://extension.umd.edu/resource/invasives-your-woodland-white-mulberry/