Debbie Arrington

Seeds: Get the dirt on building good soil

Steve Zien is among the top soil professionals and organic gardening experts in the Sacramento area.
Steve Zien is among the top soil professionals and organic gardening experts in the Sacramento area. Sacramento Bee file

The key to a better garden is right under your toes.

Start loving your soil, instructs Steve Zien, and stop treating it like dirt.

“We know more about things a billion light years away than about what’s happening six inches under our feet,” said the Citrus Heights-based founder of Living Resources Co., which provides soil and organic gardening consulting.

Zien preaches and practices eco-friendly methods that can help any landscape cope better with drought while resisting pests and disease.

He starts with building soil into the sort of environment that promotes healthy plants. That takes patience. Months may be needed to re-establish helpful microbes, which are single-cell organisms such as bacteria and fungi that make soil alive and not just dead dirt.

Made up of sand, silt or clay, “dirt” – the actual mineral material – makes up about 49 percent of soil content, Zien explained. Fifty percent of soil is actually pore space – the important little gaps between particles – that hold air and water. That leaves 1 percent for organic matter including dead roots, live roots and living organisms such as those hard-working microbes.

“Think of land not as a commodity but a community,” Zien said. “One tablespoon of healthy soil has more living organisms than there are people on the earth.”

Those tiny microbes help plants grow better through symbiotic relationships developed over eons. They form the glue that holds together “soil structure,” including those pores for air and water storage. They can break down and store important nutrients such as nitrogen, then help roots find them. As part of their complex partnership, microbes fight plant diseases and prevent pest infestations.

And they can make gardening a lot more productive with a lot less work.

“Plant roots stimulate and regulate soil biology,” Zien said. “Roots produce chemicals that tell the microbes to do different things. They work together. But the microbes have to be there.”

The problem? Many gardeners, often inadvertently, have killed off those beneficial microbes by the zillions, Zien said. Instead of fostering their slow progress, gardeners wipe out these friendly organisms through indiscriminate use of synthetic fertilizers, herbicides and pesticides.

In turn, those quick fixes can destroy healthy soil and turn it into lifeless dirt, Zien said. That makes plants work a lot harder just to survive.

Before searching for chemical solutions to plant problems, first ask yourself: What would Mother Nature do?

“You don’t see her reaching for chemical fertilizers or sprays,” he quipped. “So why should you?”

Although organic gardening methods have been around for millenniums, soil scientists are still discovering more about the complex bonds between microbes and plants, Zien said.

An example is frankia, nitrogen-fixing bacteria that form nodules in plant roots. Nitrogen-fixing bacteria turn atmospheric nitrogen into solid nitrogen compounds that plants can use to feed their growth. After eons of evolution, frankia are very common in California native plants, Zien said, and the secret to their drought-busting success.

“Frankia can take nitrogen out of the air,” Zien said. “That air, of course, is below ground in the large pores of good soil structure. That (nitrogen) supplies almost all of the plant’s fertilizer needs. The frankia also store water. That helps these natives survive drought.”

Frankia – or lack of it – is at the root of problems that may develop with native gardens, Zien explained. Most non-native plants can get by without frankia, but this bacteria is vital for the health of California native gardens.

“We’ve seen a lot of people replace their lawns with California natives during the drought,” he said. “The plants will grow fine, but two or three years later, they start to die. Why? A lot of homes around here were built in the 1950s and ’60s. The first step for those subdivisions was removing the top soil (as sites were leveled).

“When they removed the top soil, they removed the frankia,” he added. “The roots of those California natives are not getting enough frankia and they become stressed. You need to build it back up. That means inoculating your soil with native soil that still has that frankia, from some place such as the foothills – not agricultural land – that still has its top soil and where you see natives thriving. Just remember: Always ask the landowner first before you start digging.”

Gardeners can promote healthier soil from the top down, he said.

“Most soil has about 1 percent organic matter,” Zien said. “Ideally, you want 5 to 10 percent organic matter.”

For starters, Zien said, spread organic mulch – such as compost, shredded leaves or cut grass – over the top of the ground. Don’t dig it in, but let it naturally break down and feed those microbes below. Earthworms – “nature’s fertilizer factories” – move the slow process along by digesting organic matter and pooping out root-ready nutrients, he added. Over time, that passive blanket of mulch will nurture a healthy underground community.

“It’s a symbiotic relationship,” Zien said. “Healthy soil grows healthy plants.”