Strip Cultivation Tips for Weed Control

Over the last three decades, the use of herbicide strips has become a popular horticultural practice among apple growers. Herbicide strips can reduce or eliminate weed competition with trees, and also help improve orchard sanitation.

However, the practice of making herbicide strips can also increase chemical costs, while leaving bare soil prone to erosion and nutrient loss. In addition, they can reduce habitats for beneficial insects.

These costs, coupled with more growers turning to organic pest control options, has led to increased consideration of strip cultivation within the drip line and tree row as another weed control option.

Results: Economics
$$/Acre	Herbicide(1)	Wonder Weeder + 3 Point(2)	Wonder Weeder(3)	Grower Built Cultivator(4)
Tractor	$13.37	$13.37	$13.37	$13.37
Equipment	$2.50	$5.00	$3.25	$1.50
Herbicide	$50	NA	NA	NA
#Applications	2	4	4	4
Total	$131.74	$73.48	$66.48	$59.48
Savings	NA	$58.26	$65.26	$72.26
Equipment cost estimated at: 1) $2,500; 2) $10,000; 3) $6,500; 4) $3,000 Estimated floor management costs based on 10 year cost of ownership for a 100 acre orchard assuming: a 75 hp tractor, 10% yearly equipment maintenance and application time of 0.26 acres/hour.

In order to assess the benefits and costs of this type of weed management approach, a team of Michigan State University researchers led by Matt Grieshop, Ron Perry, and Krista Buerher has been holding trials at three different sites in the state. The trials are designed to evaluate a cultivation system’s impact on weeds, nutrients, and tree growth, the effect on beneficial pests, and the relative production costs of such a system.

Three orchard sites were selected in Flushing, Pottersville, and Sparta, MI. The Flushing site included mature trees under strip cultivation for more than five years, the Pottersville site was fifth-leaf trees under a dormant herbicide, and the Sparta site was based on fifth leaf trees under a burndown herbicide.

The sites were cultivated once per month from May to August. The Sparta and Flushing sites were cultivated with a Wonder Weeder implement, while the Pottersville site was cultivated with a grower-built implement. Researchers made monthly weed measurements on three cultivated rows and three standard rows. They also collected soil and leaf nutrient samples, and measured mite counts as well as terminal tree growth.

Promising Results

Based on the research, cultivation greatly reduced ground cover compared to no treatment. Cultivation was comparable to burndown herbicides, while preemergent herbicides resulted in less ground cover.

Weed biomass in terms of dry biomass ounces was also considered in the research. Biomass on the cultivated sites was significantly reduced compared to no herbicides, while the biomass was comparable on sites with herbicide treatments.
Soil organic matter was measured during August. Cultivation resulted in slightly increased soil organic matter at all three sites. Increased soil organic matter should reduce nutrient leaching and increase water holding capacity. However, change in soil organic matter is a slow process, so these results are preliminary.

In terms of tree growth, cultivation may impact young trees more than adult trees. There was no significant impact at two of the sites, and all plots demonstrated acceptable growth.

Researchers also looked at the effect of cultivation on beneficial mites. At two of the three sites, predatory mites were more abundant in cultivated rows compared to non-cultivated rows. The increased plant material in the cultivated rows may have increased the level of beneficial mites.

The Bottom Line

So what might cultivation mean for your bottom line? As you can see by the chart on page 42, savings per acre could come close to $75, according to researcher estimates. However, the number of times you pass through each row may have an influence.
Cultivation can provide a largely comparable level of weed management, while potentially being less expensive than traditional means of weed control. Both weed coverage and weed biomass can be reduced, while growers may see an improvement in soil organic matter and beneficial populations.

However, there is still more work to be done in this area. Future goals for the research team include continuing soil, tree, and fruit measurements, determining impacts on yields, assessing the potential of combining orchard operations such as cultivating and mowing, assessing impacts on rodent populations, and identifying additional implements.