 |
|
|
|
| |
The Garden Plot for September 21, 2007
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: “Weed Ecology”
If we’re honest about our gardens, we know they’re not just all about our plants. Gardens are really a system of crops, impacted by soils, soil microbes, insects, weeds, disease, soil and air temperatures, water, shade, and sunlight. We are finishing a weed ecology study on my farm this year that looks at weeds from this kind of systems approach. First we asked which gardening practices promote weeds. Here are the big three culprits that force us onto the weeding treadmill:
Disturbance – tillage releases nutrients (like nitrogen, the turbo-jet for most weed growth). Tillage and weed cultivation creates bare soil that just screams for something to fill it.
Monoculture – growing one or a few plants leaves unfilled space for pushy weeds to fill. Single species plantings rarely use all the moisture, nutrients, and light available. Weeds are glad to share what is not used.
Profligate fertilizer and water use – Create excess and weeds will come!
Second, we set up a study to minimize these practices. Our system treatments were chosen to:
Minimize disturbance. We grew a no-till clover living mulch in between crop rows. Within crop rows, we tested no-till and minimum tillage treatments. The minimum tillage treatments included application of black paper mulch, vinegar, and a single minimum tillage in the spring, then allowing the clover living mulch to grow in underneath the crop.
Design for plant diversity. Some of our treatments were chosen to fill in most, or all of, the below and above-ground spaces around our crop.
Minimize fertilizer and target fertilizer application to desirable plants only. Most of our treatments received only a minimally tilled clover green manure in the spring. Some treatments received green manure clover plus compost. No fertilizer was applied to areas between crop rows.
We looked at the effect of these treatments on soil fertility and plant nutrient cycling, soil temperature, insect and disease pests, and crop growth. Crop plants grew best in the minimum-till treatments with compost added, as well as the black paper mulch and vinegar treatments. Yields in the minimum-tillage plus paper mulch and vinegar treatments grew better or as well as the control treatment, in which crop plants were kept free of vegetation April through August using normal weed cultivation, such as tillage and hoeing. Plant growth and yield were lowest in the no-till and minimum-till without compost treatments. Lower yields were probably due to cooler soil temperatures, lower nitrogen levels in April and May, shading, and below-ground competition for space.
In summary, we may not need to be as worried about keeping our crops free of competing vegetation as we once thought. When soil fertility is high and nitrogen levels are adequate and easily available to crops, especially in the first part of the growing season, our plants can put up with other plants growing near them. Maybe weeds aren’t so bad. However, if we look at the garden system in the long-term, it would probably be best to choose “fill-in plants” that make good green manures and provide habitat for beneficial insects. Flowering legumes that store nitrogen, such as clovers, are the “fill-in” plants we have worked with for the past three years. Other more drought-resistant plants might make even more sense in our hot, dry climate.
The Missoula County Extension Service will be hosting a tour of our weed ecology experiment plots and the minimum-till living mulch system at Biodesign Farm on Sunday, September 23 at 1 pm. For more information on the tour and directions call 258-4213.
Helen Atthowe's new short program of gardening tips
|
|
|
