Read at :
Google Alert for gardening
Salt Lake Tribune
http://www.sltrib.com/homeandfamily/ci_6440559
Gardening: Soil amendments that pull their weight
By Maggie Wolf
Special to The Tribune
* MAGGIE WOLF is an assistant professor for Utah State University Extension in Salt Lake County. E-mail her at maggiew@ext.usu.edu.
Nothing beats homegrown compost
The true secret to a great garden is as plain as the dirt under your nails. Healthy soil begets healthy plants. But how can you transform ancient lakebed into sweet-smelling, brown, crumbly soil? Mixing in soil amendments create a shortcut around the long road to organically rich soil, but amendment has strengths and weaknesses. Choose the route that best suits your soil, site, time and budget. Here’s a brief rundown:
Humates
Humates are mining industry products containing humic acids. Because humic acids are also produced during organic matter decomposition, humates have been marketed as a soil “activator.” Scientific studies, however, show little evidence that humates boost crop yields or improve soil structure.
Inorganic amendments
Vermiculite, perlite, utelite and pumice amendments can help aerate heavy soil. Most are chemically inert and sterile. These products are most helpful in raised beds to assure good drainage.
Sphagnum peat moss
To lighten heavy clay soil and lower pH, sphagnum peat moss is a serviceable soil amendment. This material is used in potting mixes because it can hold water and provide aeration at the same time. It decomposes very slowly and maintains its original mass, but does little to improve soil structure. Dry sphagnum moss repels water. If you add much sphagnum to a garden bed, be sure to mulch the soil surface to help prevent water runoff.
Organic mulch
Pine bark, wood chips, shredded leaves, grass clippings, straw, sawdust, pine needles and other plant-based mulch materials can serve as soil amendments. As they decompose, they shrink in size dramatically. Some gardeners feel frustrated that this organic matter “disappears.” But as soil organisms process these materials, soil particles aggregate and soil structure improves. Dry brown mulches like wood chips or raked leaves have a high carbon-to-nitrogen ratio, so you must add about one pound nitrogen per 100 pounds mulch to compensate and keep garden plants growing vigorously.
Compost
Completely composted organic matter is the gold standard of soil amendments. Reduced greatly from the original pile size, finished compost is dark, crumbly and has a pleasant earthy smell. Homemade compost is cheapest, but it takes considerable effort, space and time to produce a relatively small amount. Compost purchased in bags or bulk varies greatly in quality. Composted poultry litter or barn stall straw may have high salt levels. Incomplete compost may smell bad and usually has a high carbon-to-nitrogen ratio. Look for dark brown compost with particles smaller than 1/2 inch and a loose crumbly texture.
Compost may be tested by the Utah State University Analytical Laboratory; visit
for details.
“One to 2 inches of compost, mixed into soil, gives more benefit [than other amendments],” says Grant Cardon, a USU Extension soil specialist. “If you’re trying to improve compacted or re-graded subsoil that was been dug out for a basement and spread around the house foundation, it may be void of microbial activity,” he adds. Compost is rich with soil microbes that help build soil structure.
For more information, download USU Extension’s “Solutions to Soil Problems” fact sheets from www.usual.usu.edu/aboutnext/index.html
