No-till gardening feeds the soil

At bottom, gardening is all about dirt — its care and feeding, its microbes and fungi, bacteria and earthworms.

Science has gradually recognized that the soil's vibrant but delicate food web must be treated carefully to produce the best yields. Turning the soil before planting is generally conceded to be more disruptive than building it up year after year with rich natural substances.

"We lose organic matter whenever we till the soil," said Mark Alley, an agronomist and professor of soil fertility and management at Virginia Tech. "That practice adds up a lot when you think about certain areas of Virginia having been tilled for more than 400 years."

No-till growing means adding layers of plant and animal matter to the topsoil rather than plowing, shaping and otherwise disturbing it.

"It reduces runoff and evaporation losses, increases organic matter in surface soils, which increases the rooting environment for seeds," Alley said. "All this makes things more productive."

Farmers began to embrace the no-dig philosophy in the mid- to late 1970s with development of a no-till corn planter, said Brian Jones, an extension agent for Virginia's Augusta County.

"It was prompted by technical innovations along with increased farmer awareness about conservation," said Jones, who doubles as coordinator of the Virginia No-Tillage Alliance. "They were becoming concerned over how much soil they were wasting each year. Now, more than 50 percent of the state's farmers have switched to no-till."

Growers save a lot of time and fuel previously used on sod busting. "At least 30 percent of their machinery inventory had been tied up in tillage equipment," Jones said. "They sold it off because no-till requires only planters and harvesters to bring in a crop."

The same planting principles apply to backyard gardens. They vary from farm fields only in scale and in varieties grown.

The first year is the hardest for no-till practitioners. The ground must be cleared of debris, weeds and other obstructions before nutrient-rich compost and protective mulch can be used.

"Initially, some digging of perennial roots may be required," said Charles Dowding, a commercial gardener and author of "Organic Gardening the Natural No-Dig Way" (Green Books, 2007). "If the soil is full of durable perennial weeds, a long-term (smothering) mulch for a year is worthwhile. It becomes much easier thereafter."

The essence of no-till gardening is staying ahead of weed growth, not allowing weeds to seed and creating a clean plant bed with just a few weed seeds germinating, he said.

"In my garden, I manage, almost single-handed, over two acres of weed-free vegetables, fruit trees and bushes, flowers and herbaceous plants with lovely clean soil that I need to spend very little time weeding, compared to most of my neighbors," said Dowding, from Somerset, England.

Because no-till encourages the soil food web to become so active, fewer nutrients need be added, and only soils with deficiencies will require synthetic minerals, he said.

"The only additions I make are occasional rock dust, from volcanic basalt, and seaweed. I am not certain that the soil needs them but I have a feeling that many soils are low on trace elements and therefore benefit from small additions of these intensely rich soil foods," Dowding said. "Adding them to compost heaps is another way of making extra health available."

Digging up the soil to destroy weeds is a failed practice, said Jeff Lowenfels, a lawyer from Anchorage, Alaska, and co-author of "Teaming With Microbes: A Gardener's Guide to the Soil Food Web" (Timber Press, 2006). It only encourages weed growth by exposing seeds to sunlight, he said.

"Heck, we've all seen plants grow through pavement," Lowenfels said. "They don't need tilled soil. The least amount of disturbance when planting in a garden is best."

Soil, then, is a great deal more than just the granular stuff holding plants erect. It teems with life but like any vigorous thing, must be nourished.

"In organic growing situations, the gardener has to make sure the microbes are getting enough food so that they can feed the plants," Lowenfels said. "I call organic fertilizers 'microbe foods,' which is what they are."

Dowding recommends that gardeners new to a no-till system begin with a small area and experiment to find their favorite growing methods. "If it seems strange or difficult at first, do persevere, because the potential rewards are significant, especially the reduction in weed growth."

Dean Fosdick: deanfosdick@netscape.net