Healthier Rivers Through Urban Agriculture
Productive urban landscapes, if managed correctly, can reduce pollution in local watershed.
In
2010 the local nonprofit Friends of the Kaw included the
Kansas City Center for Urban Agriculture in a grant to raise awareness of water
quality issues relative to the Kansas River. In this article we hope to
contribute to that effort. Our appreciation goes to Laura Calwell,
Kansas Riverkeeper for Friends of the Kaw, for her support of KC-The Center for Urban Agriculture.
By Daniel
Dermitzel
Spring is
the time of year when the region’s Riverkeepers are particularly concerned
about water quality and stream health. With the onset of strong seasonal
rains comes the risk of sewer overflows from combined sewer systems throughout
the Kansas City Metro area, and the result is increased pollution of our
creeks, streams and rivers.
The growing
popularity of urban agriculture presents an opportunity to reduce the amount of
water and pollutants entering our combined sewer systems. Urban farmers
and our community as a whole have much to gain from implementing a few simple
techniques to reduce runoff and pollution of our urban watershed. Our
productive urban landscapes (i.e., farms and gardens) have the potential
to be more environmentally friendly than the many chemically treated lawns and
unproductive green spaces we currently see throughout our city. Converting a lawn to an organically managed agricultural landscape can promote
a healthy environment and capture ecosystem services (such as food production)
which were previously underutilized. But to realize these benefits, it is
important that we keep several key design principles in mind as we build our
urban farms and gardens.
1. Soil Management
From the
perspective of storm water management, an important benefit of creating
productive urban landscapes is that farmers tend to reduce soil compaction in
the process. Storm water runoff is aggravated by the many impervious and
compacted pervious surfaces in our cities.
Urban
farmers generally work hard to reverse soil compaction and create spongy, loose
soils for their crops to thrive. High organic matter content is
particularly beneficial to plant health and also increases the soil’s nutrient
and water holding capacity. But once we have created healthy soils, we
have to prevent them from being eroded or compacted again.
On small
urban operations, farm-scale mulching is both feasible and very useful. Under the protective cover of mulch soil is less subject to erosion and
compaction by heavy spring rains. However, mulch can slow down spring
soil warming and farmers may decide to delay applying mulch until after the
soil has warmed up sufficiently.
Special
attention is often warranted when farming on slopes; building terraces,
contour farming and alternating permanently planted green strips with growing
beds are techniques that have been widely used to control erosion on
large-scale farms and may be appropriate for small urban farms as well. Also, all farmers should consider ways to minimize tillage as it tends to
degrade the soil and create a new layer of soil compaction a few inches down.
2. Nutrient Management
The loss
of nutrients from farms and other sources is responsible for such ecological
disasters as the Dead Zones in the Gulf of Mexico and elsewhere. Nitrates
and other chemicals run off cropland and animal feeding operations and
accumulate in our streams which carry them to the ocean. There they cause
spikes of algae growth which lead to oxygen depletion and massive fish
kill. Urban farmers should avoid contributing to this problem and apply
fertilizers in modest amounts, especially synthetic fertilizers which are
highly soluble and easily carried away with runoff. Instead, they may
wish to consider organic fertilizers such as compost, well-rotted manures,
alfalfa pellets, rock phosphate and similar products. These will stay in
your soils longer and release their nutrients more slowly.
Regular
soil nutrient testing may be a valuable tool to determine the amount of
fertilizer needed and to monitor soil health over a period of
years. Using soil test results as well as historical yield data and
taking into account any nitrogen fixed by legumes, urban farmers can determine
appropriate fertilization levels and avoid over-fertilizing their gardens and
fields.
3. Pest and Weed Management
According
to information published by Friends of the Kaw, the chemical atrazine is one of
the most commonly used herbicides in the US. It is regularly applied to
corn as well as lawns, parks and golf courses. The chemical has found its
way into our drinking water supply causing some to be concerned about adverse
health effects.
Urban
agriculture provides an opportunity to take land stewardship seriously in our
backyards, vacant lots and other urban green spaces by reducing or eliminating
the use of synthetic pesticides and herbicides. Fortunately, it is our
experience that the majority of urban farmers uses sustainable or organic
practices. For those who feel they must apply synthetic chemicals to
their urban fields we suggest following all application instructions on the
product label and creating vegetative buffer zones to filter contaminated
runoff and reduce chemical drift.
4. Irrigation Practices
Finally,
we can serve our streams and rivers by adopting water conservation
practices. These include harvesting water wherever possible from nearby
roofs or trapping it in infiltration swales on sloped terrain. Both
measures will reduce the amount of water that runs off the site—therefore
lowering the burden on the combined sewer system and possibly reducing overflow
events—and also lower the farm’s irrigation bill. However, in a few cases
water running across an urban farm may have been contaminated by sources
upstream. Such water may not be suited for irrigating food crops
and may best be diverted from them.
The
benefits of mulch have already been mentioned but bear repeating here. A
layer of mulch will trap rainwater and reduce runoff in addition to reducing
the need for irrigation during the hot months of the year. And finally,
drip irrigation is a practice which gives the farmer more control over how
water flows across an urban farm. The lines slowly deliver the water
directly to the crops’ root zone, usually without puddles and unwanted runoff;
and the lines can be placed under a layer of mulch where evaporation levels are
low.
The above
techniques are just a few of the steps urban farmers can take to protect the
health and quality of our urban watershed and of the streams and rivers
connected to it. As we become more productive and ambitious as urban
farmers, it will be helpful to spend some time on reviewing our water
management strategies and to control the movement of soil, nutrients,
potentially harmful chemicals and, of course, precious water from our urban
farms. In doing so we will become more connected to the land we farm and
better stewards of the natural resources around us. That—in addition to
our fresh vegetables—is definitely something worth sharing with our neighbors.
My
thanks to the authors of "The River Friendly Farm--Profitability, Stewardship,
Qualify of Life" (published by K-State Extension) whose paper
was a valuable resource in compiling this article.
You can read the June 2011 edition of Cultivate, the Kansas City Urban Center's e-newsletter at
http://www.cultivatekc.org/urbangrownjune2011.html
Reach
Daniel at daniel@kccua.org
