Feasibility of Agroforestry System using Management Intensive Grazing in Eastern Black Walnut Plantation
The overall objective of this demonstration/research project is to determine if, and how much, yearling steers will damage black walnut trees while grazing in a plantation setting. A more specific objective is to determine the effects on both trees and forage when cattle are rapidly rotated through a series of small paddocks using a management-intensive grazing system in a black walnut plantation.
In April 1999, 26 head of 575-pound steers were placed on 20 acres of pasture divided into 16 paddocks. The paddock divisions were accomplished with electrified polywire and step-in posts. Only 12 of the paddocks contained black walnut trees. The remainder contained big bluestem, a native warm season grass for summer grazing only. For the first few months, the cattle were rotated on a daily basis only through the 12 tree paddocks. The system expanded to 16 paddocks in June with the addition of the big bluestem.
During the 90-day grazing period, it was noted that the cattle established a browse line on the lower tree branches about 6 feet above the ground. Smaller trees (less than 8 feet tall) were severely damaged by browsing because the cattle often destroyed the central bud or main growing point of the tree. Rubbing damage was most noticeable on small trees, especially those that cattle could use for scratching their heads.
Preliminary observations indicate that trees 10 feet tall or more will not be adversely affected by browsing to the 6-foot height since this would be a normal level for pruning. Experience with use of the electric polywire indicates that running a temporary fence down each side of the tree row can inexpensively protect smaller trees.
In April 2000, 25 steers weighing an average of 615 pounds were turned into the demonstration area in the same manner as in 1999. Results and observations were similar to 1999. Tree growth will be measured again in spring of 2001, after which a final analysis and report will be made.
First-year results are promising for this agroforestry system that will allow cash flow from cattle grazing during the establishment years of the plantation.