Low Environmental Impact Establishment of Hybrid Poplar Plantation

PROJECT BACKGROUND
The operation that accepted this grant has a large percentage of marginal lands that are in use of rotational crops. Crops that I raise are hay, corn, what and barley as cash crops or as livestock feed for the sheep operation. These production lands are in an environmentally sensitive waterfowl production area.

Over the last several years, we’ve planned some Hybrid Poplar trees as a possible alternative crop. Our plan is to perform land preparation and weed control using mechanical means with no chemicals.

PROJECT DESCRIPTION AND RESULTS
The goal that I am trying to achieve is to establish a hybrid poplar plantation using only mechanical means for land preparation, weed control and alternative fertilization methods for reduced environmental impact on marginal lands.

The 10 acres of marginal land selected for this grant was used for rotational crops and was suited to this type of production six years out of ten because of wet conditions. We will be observing three varieties to analyze performance.

My partner and I began planting hybrid poplars four years ago. The choice of trees at that time was based on direct input from other producers, information from the DNR, local paper mill, and University of Minnesota. Each year that trees were planted we were able to learn rates of growth, resistance to drought and flood, resistance to disease by direct observation.

Groups and individuals that have assisted with this project were as follows:
- Joe Dooley, Board Member, Minnesota Agroforestry Coop, provided information on varieties of trees.
- Schumach Nursery provided the hybrid poplar sticks/cuttings
- John Arnold, farmer – helped select the land based on previous yields in corn and soybeans
- Chick Rick and Dave Johnson, District Conservationist, evaluated the environmental impact of the project
- Steve Vongroven, MARC&D Forester, had a site visit and developed the production plan
- Dave Schwartz, University of Minnesota Extension Educator, was a consultant for pest/disease control and 4-H liaison.

As in years past, the preparation of the land, planting of the trees, management of weeds was done completely by mechanical means. After planting, the field was worked by mechanical means for weed control as early as consistently as possible. The most often used piece of equipment used for mechanical weed control was the cultivator. A pre-emergent herbicide was not used to prepare the field prior to planting. Post emergent herbicides were not used to keep the field clean. The herbicides currently available have carryover for several seasons which tends to stunt the growth of the trees for several years based on anecdotal evidence.
The 10 acres set aside for this grant was laid out in a 10 foot by 6 foot wide grid pattern. This enabled two tractors to be used, one set up for the 10 foot wide row and another set up for the 6 foot wide rows. The reason it was set up this way is so that two persons could be cultivating simultaneously and each row would require only one pass with the cultivator to clean the row to full width. This reduced the number of man hours required for cultivating and reduced the risk of disturbing the developing root system of the hybrid poplar sticks/cuttings.

In previous years, the trees were planted in an eight foot by eight foot grid. To use mechanical methods of weed control, a small tractor with a 4 foot wide cultivator was used which required going down each eight foot row twice to clean the row to full width. There was a lot of man hours required using this method and hybrid poplar sticks/cuttings were disturbed because of the high frequency of passes that had to be made to clean the field.

Regardless of which pattern was used to lay the trees out, many factors affected the ability to use mechanical means for weed control, fertilization and pest control. Availability of equipment, soil moisture, and availability of labor also affected the frequency and consistency of mechanical means for weed control. Early in the season, the 10 acre field was very wet and didn’t allow for access to the field but the excess moisture also prevented weeds from emerging. As the field dried, the weeds soon emerged and quickly out paced the trees. Regular cultivation is ideal in this situation to reduce the competition between the trees and weeds but is very difficult to do with other field work. In the fall, the trees demonstrate the benefits of avoiding chemical management. The trees appear to do a significant amount of growth in August, September and into October. Often times the weeds that could not be eliminated through cultivation during May, June and July begin to die off and don’t compete with the trees during this growth spurt. In the spring of the second year, the trees are standing taller than the weeds and cultivation is easier due to the increased visibility of the trees. Mechanical methods of weed control will be required in the second year of growth. By the third year, the trees from a canopy, which reduces the competition naturally and therefore decreases the amount of time spent required for weed control.

In conclusion, the first growing season is the most difficult for using mechanical means for weed control. Wet weather played a large part in the inability to get into the field and cultivate the weeds just when they have emerged. By the time the field was dry and cultivation can begin, the trees were covered by weeds. Herbicides looked very inviting at this point as a means of weed control, especially when a field is planted in trees but they can’t be seen for the weeds. But by year two and three, any differences will quickly evaporate. By using mechanical weed control, there is no carryover of any chemicals, and the trees actually do better in the following years than those who had been exposed to chemicals, based on anecdotal evidence.

OUTREACH
Brochures were developed and distributed to Minnesota Extension Office, which includes the 4-H clubs, and the Meeker County Soil and Water Conservation Office.

As a member of the Minnesota Cooperative, the stands of Hybrid Poplar will be made available on an ongoing basis for field days, tours and new member educational purposes. The Minnesota Agroforestry Cooperative will be a resource as the trees become ready for harvest.