WW-06187     1993  

Performance of Shrub Species as Field Windbreaks Under Center-Pivot Irrigation

MEASUREMENTS AND EVALUATIONS

Measurements and evaluations were performed for each test plant at the end of every growing season. They were evaluated for survival, vigor, height, spread, disease and insect damage, animal damage, and general suita-bility for use under center-pivot irrigation systems. Seven growth characteristics were considered when evaluating and selecting shrub species for planting under center-pivot irrigation systems:

1. Crown spread—the crown spread of a particular species determines the amount of land that would need to be taken out of crop production to provide for the mature shrub. A rule of thumb is that the crown width should not exceed shrub height. A compact, columnar form is ideal.

2. Height—the eight-foot to twelve-foot high traveling irrigation booms must clear or slightly bend the tops of the shrubs without breakage to the plants or damage to the pivot system.

3. Root suckering—suckering can cause excessive width to the windbreak, particularly if normal cultivation near the windbreak will not control its spread, providing competition and harvest problems with crops being grown in the adjacent field.

4. Maintenance—shrubs should require little or no pruning. Weakness of stems, the angle of branching, and its susceptibility to snow breakage must be considered.

5. Tolerance to herbicides—the windbreaks will be on intensively farmed land and will be subjected to a variety of herbicides. Sensitivity to herbicides will reduce plant vigor, effectiveness of the windbreak, and cause potential disease problems.

6. Cold tolerance—species must be adapted to the extremely cold temperatures encountered in Minnesota.

7. Overall condition—each plant was rated as excellent, good, fair, poor, or very poor.

Each of the test species was evaluated during the annual meeting of all cooperators. The group decided which species to continue testing; which species, if any, should be removed; what new species should replace terminated species; and which species, if any, should be recommended to the farmers for planting under center-pivots. In late April or early May of each spring, any species selected for termination was removed and replaced with any selected new species, furnished by the USDA Soil Conservation Service, Plant Materials Center, Bismarck, North Dakota.

During the 1984 and 1985 growing seasons, almost all activities on the Herman Rosholt Research Farm ceased because of budgetary problems. This included a shutdown of the irrigation system. Although those two growing seasons were not exceptionally dry years, all shrub species showed symptoms of drought damage to varying degrees. In 1986, the Pope County Soil and Water Conservation District Board, led by Chairman Dave Jellum reinstated research activities and turned on the irrigation system for the shrub plots.

Species Tested

The planting stock was provided by the Soil Conservation Service Plant Materials Center located at Bismarck, North Dakota. Most of the planting stock came from known seed sources. The original planting on May 1, 1979, included 16 shrub species and two tree species. Table 2 notes in alphabetical order, and by planting date, each of the species that were discontinued, the reasons for being discontinued, when they were removed, and whether and by what each was replaced with. The performance of these species at the time of removal is summarized in Table 3.

Table 4 notes in alphabetical order, and by planting date, characteristics of species still being tested through the 1989 growing season when the project was terminated. The table includes comments relative to the performance of each species. Table 5 summarizes the performance of these species at the project’s termination.

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