Callaway County
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Jarman's Weekly Agronomy News February 23, 2000 |
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Color Your Garden for Better Production |
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There was a gardener who wanted to know what kind of carpet grew the best tomatoes. It seems he was using carpet scraps to mulch his tomato plants. Some of the tomatoes seemed to grow and produce better, larger tomatoes. Yes, ask your local agronomist. My non-answer answer was that he seemed to be the expert and obviously knew more about carpet mulching tomatoes than I knew. I even went to see his tomato patch. Still, no answer on why some tomatoes did better with certain types of carpet. Now, I may have found the answer. Not whether a Berber is better than a shag or natural backing was better than synthetic. It was probably the color. The bright red carpet was a color that I remember. Recent USDA, several Land Grant Universities and other countries have been doing research in the differences between different color and other characteristics of mulch. One piece of research that stood out was that tomatoes produce quicker and larger fruit with red colored mulch. This has already become a commercial product. Watch your gardening catalogs different colored mulches. Unfortunately, as with many new and better products, it costs more. The old standard plastic mulch was black. It is tough and sun resistant. Some of the advantages of a mulch are: 1) increased soil temperature; 2) reduced soil compaction; 3) reduced fertilizer; 4) reduced evaporation (but mulching is NOT a substitute for irrigation); 5) cleaner produce (elimination of soil splashing); 6) reduced weed problems, (clear plastic will allow weed to germinate); 7) earlier crops, (black plastic mulch can give 2 to 14 days earlier production from warmer soil); 8) increased growth,; (high levels of CO2 build up under the plastic - It comes through the holes made in the plastic for the plants and localizes CO2 for the plant). The disadvantages are mulches are costly - there is a greater initial costs, increased management since the mulch moisture must be carefully monitored to be successful, and increased soil erosion in the middles between plastic strips. Plants have been found to be most sensitive to blue, red and far red (near infrared). The reason we see green is because that is the wavelength of light the plant is throwing away. By manipulating these colors (wavelengths), different growth patterns can be enhanced or retarded. There have been tests on mulches of red, orange, yellow, blue, green, white, aluminum, black, and clear on peppers, cotton, soybeans, southern peas, turnips, potatoes, and tomatoes. The combinations of colors to plants is really complicated. These advantages can be enhanced through the use of different colored mulches. Red has already been mentioned. It reflects wavelengths of light that enhance the top growth of tomatoes increasing harvest by 10% to 15% over black. Cucumber with a red mulch had increased yields of 18%. Silver aided peppers with increased yields of 22%. Squashes produced 14% more with blue or red. Pale blue or white has been found to enhance root growth and increased the production of potatoes by 15%. Japanese research on carnations with reflective mulch gave a 33% to 107% increase of flowers cut. Unfortunately, yellow mulches tended to attract certain insect pests. Still, it looks like solid, reliable recommendations for what color for what plants are a few years away. Another question is the plastic mulches have advantages in reducing pest problems without the use of pesticides, but are they organic. Some organic certification organizations say yes and others say no. This is another question on the use of plastic mulches that we need to wait on for a final decision. They have large advantages that are hard for commercial and home gardeners to ignore. Information for this article came from USDA-ARS, several University, and commercial gardening web sites. (Jim Jarman, 573-642-0755, jarmanj@missouri.edu)
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