LAND IMPRINTING FOR ECOLOGICAL WEED CONTROL THROUGH
ACCELERATION OF SECONDARY SUCCESSION

October 5, 2003

R.M. Dixon

Weed control involving soil disturbances, as commonly employed in agricultural practices and elsewhere, tend to perpetuate the weed problem indefinitely into the future. These include pulling, hoeing, grazing, blading, cultivating and herbiciding-all practices that disturb the soil, thereby ensuring another crop of weeds that depend on such disturbances to become established. This vicious circle of weeds thriving on the control method can be interrupted by using strategies that have some basis in ecology. These include the judicious use of mowing, no-tilling, seeding and heat. An appropriate combination of mowing, no-tilling and seeding can often displace the weeds through the natural succession of plant species. That is, exotic weeds can be replaced by native plants that occur later in the natural succession. Such native plants tend to be longer lived and taller growing which gives them a survival advantage over the weeds.

Methods involving heat including flaming and steaming provide only temporary control unless combined with no-tilling and seeding.

Now let's apply ecology to the problem of fountain grass control in Shadow Roc . (a)

The three-step procedure is:

•  Create a surface mulch of the fountain grass top-growth using a line weeder after the weather cools in November.

•  Scatter a mixture of seed including 4-wing saltbush and native wildflowers on top of the mulch.

•  Scatter some peat moss on top of the seed.

The function of the fountain grass mulch is to suppress surface evaporation, suppress regrowth of the fountain grass, and enhance growth of the new seedlings. The purpose of the seed mix is to replace the fountain grass with more desirable native species. And the function of the peat moss is to cover the seeds while building topsoil for the new vegetation.

The foregoing 3-step procedure can be augmented by making several indentations in the soil about one foot apart to funnel resources together in the bottom of the depressions where they can work in concert to germinate seeds and establish seedlings. An appropriate tool is the hand imprinter that requires some moisture in the soil to function properly. The hand imprinting should be done after the 3 steps and following the first good rain.

As mentioned above, the fountain grass mulch suppresses regrowth. This is by blocking light and cooling the soil. The grass crowns can be killed by covering with a wet blanket of newspaper thick enough to shut out all light. The newspaper eventually biodegrades into beneficial topsoil.

The 3-step method for controlling fountain grass is hydrologically beneficial as it increases soil surface cover, increases rainwater infiltration and reduces water runoff and erosion. Downslope flooding and sedimentation are also reduced. On the other hand, control methods that disturb the soil are hydrologically detrimental. Other exotic plants (weeds) may be controlled in a similar fashion as outlined here. Annual weeds are much easier to control than the perennial example given here.

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(a) Shadow Roc is a subdivision north of Tucson , AZ in the foothills of the Santa Catalina Mountains where fountain grass has colonized some areas enough to present a fire hazard.

Land imprinting controls weeds by accelerating the secondary succession past the weed stage.
Photo: Prototype imprinter turning tumbleweed into a beneficial mulch in Avra Valley , Arizona

Citation: Dixon , R.M. 2002. Ecological Weed Control: Fighting Plants with Plants. IF Essay 06 June 03. The Imprinting Foundation, Tucson , AZ.

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