Sustainable Agriculture Research:

Soil Restoration is the Key

Spring Valley Ecofarms is not a farm in the conventional sense.  Rather, it is an incubator of ideas for sustainable agriculture, a place ideas can be tried out to see if they offer potential for sustainability. Graduate students have carried out projects lasting for three or four years, and once their research is finished, they move on and other students begin new projects. Some projects are long term, such as Dr. Jordan's forest management trials. However, all research projects have been focused on ecosystem management that is sustainable, through research on soil restoration and on increasing the efficiency of nutrient cycling and energy flow in both crop and animal systems. Visitors to Spring Valley Ecofarm will not see all the projects described, but only those currently underway.   

Topics on this page (click the Titles for quick navigation)


Annual Vegetables




Other Conservation Measures

Forest Management

Conserving Biodiversity


Annual Vegetables

Fertilizers are one of the most energy expensive inputs into agriculture. Energy savings occur when plant materials instead of commercial fertilizers are conserved and added to beds of vegetable crops. The plant residues add nutrients as well as serve as a food source for microorganisms that conserve nutrients and improve soil properties.

Alley Cropping


Alley cropping is a farming system in which crops are planted in “alleys” between hedgerows of leguminous shrubs. The idea is that when the shrubs are pruned, nitrogen rich leaves and stems fall into the alley, decompose, and fertilize the crops. We found that the fertilization effect reached only a foot or so into the alley, and that root sloughing from the shrub contributed more nitrogen to the soil than did the leaves. More important functions of the hedge row are to provide habitat for beneficial spiders, and to act as barriers against deer that want to feed on our crops.

Alley cropping with hedgerows of Amorpha fruticosa
Click image above for larger view

Conservation Tillage

Plowing the soil to reduce weeds and loosen the seedbed before planting results in oxidation (loss) of soil organic matter. Conservation tillage involves planting a winter cover crop, rolling it flat in the spring, and planting crops in the mulch. The mulch adds organic matter to the soil, and increases available nutrients for the crop. A no-till planter is used to insert vegetable starts through the mulch. The planter works best on flat terrain and in soil that is smooth.

No Till Vegetale Planter
A no-till vegetable planter
Click image above for larger view

Conservation Tillage

Roller crimper to flatten crop
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An alternative to roller crimping is to mow the cover crop, and then use a “spader” that uses reciprocating spades to push the residue into the soil. Spading conserves organic matter by burying it, but it must be followed by rototilling to smooth the soil for planting with vegetable planters and direct seeders. Spader

A spader in operation
Click image above for larger view




Adding compost to vegetable beds is a traditional way to build up soil fertility. We made compost from a variety of resources from the farm, including cow and horse manure, chicken litter, hay, and rotten vegetables.


Students in the Maymester Class learning to build compost piles.

Cover Crops as Energy Savers

Cover crops can enrich the soil, and when interplanted with economic crops, can suppress weeds. With clover as a cover crop, there is little need for fertilizer or for mechanical weed control. At Spring Valley Ecofarms, we interplanted crimson clover in the fall with kale and oats. As long as the economic crop has a head start, the cover crop does not compete.


Crimson clover planted as a cover crop under kale. The clover enriches the soil with nitrogen and helps suppress weeds. Crimson clover planted in the fall along with oats. Both crops become established and grow just a few inches before winter. In the spring, the crops begin vigorous growth. This photo was taken in late March. The oats will be harvested by hand for our horses, and the clover will be spaded into the soil.


We are also experimenting with a “living mulch” system developed by the University of Georgia, College of Agriculture. White clover is planted in the fall, and in the spring, bands are created in which economic summer crops are planted. We will be planting vegetables instead of cotton.

Pictured at right: Cotton, planted in bands between living mulch (white clover) at the University of Georgia Agricultural Experiment Station.




Perennials are much better adapted to the Piedmont soils because once they are planted, they do not require cultivation.  Soil organic matter (condensed energy) is conserved.  Areas between bushes is planted in grass.  Mulch or compost is added only around the base of the plant. 

Shade Grown Blueberries

In Central America, coffee is sometimes “shade grown”, that is, the coffee bushes are planted under a thin canopy of forest trees.  The beans ripen more slowly this way, and supposedly give a better taste.  We have tried “shade grown” blueberries grown under  pine and paulownia.  Root sloughing from the paulownia adds organic matter to the soil. Pine needles increase soil acidity that favors blueberries.

Blueberry bushes in the fall under a thin canopy of paulownia and pine

Organic Vineyards

We established a half/acre vineyard with several varieties of grapes. The trellises were constructed of metal “t posts” and pvc cross arms so that the grapes would be organic (treated wooden posts are not allowed organically). Wire to support the vines was strung along the end of the cross arms. While fruit formation was good, every year birds destroyed most of our crop. We experimented with various types of bird netting to no avail. As of 2015, we are trying bird netting stretched completely over the vines and down to the ground on both sides, and supported by a pvc hoop.

Metal t-post with pvc cross arm supporting muscadine and European grape vines

Organic Fruit Orchards

We were told that it was impossible to grow organic peaches in Georgia, because of the plum cucurilio ( Conotrachelus nenuphar) and many fungal diseases. Our first season, we were moderately successful in growing peaches with organically approved pesticides. (Spinosad) and fungicides (Serenade). However, we could never repeat that partial success. We also have fared poorly with apples, because of the presence of many red cedars on the farm, host to a fungus that attacks apples, and because of predation by birds.



The breeds of cattle favored by most ranchers in Georgia are not well adapted to ecosystems where the natural vegetation is forest, not grassland. We have experimented with “Intensive Grazing Management” which may help overcome the ecological difficulties. In this system, cattle are frequently moved to ensure that grass is maintained at its most productive stage. The most productive stage of grasses is when they are between 2 and 4 inches in height. If they are grazed below that, the roots become starved. Higher than that, the grass becomes coriaceous and difficult to digest. To keep grass at the most productive stage, cattle are grazed intensively on a small pasture for only a few days and then are moved before they overgraze. A problem often is ensuring water availability for the cattle in each of the pastures. Ideally, the pastures are shaped like pieces of pie, with a water source in the center.

Cattle ready to be moved

Free Ranging Hogs

They ranged freely within a stand of young oaks. As piglets, they learned to respect the electric wire fence. In order to sell meat to the market, the animals have to be killed and dressed in a U.S.D.A. approved slaughter house. The nearest approved facility to Athens is in Augusta, a four hour round trip that makes the effort uneconomical. We killed and cleaned hogs ourselves for holiday pig roasts.


Pasturized Rabbits

Meat rabbits usually are kept in small cages that prevent movement. We tried another approach that allowed the rabbits more freedom of movement.

There were several problems with this approach.

  • It was a lot of work to move the cages 
  • Ants were a problem.
  • They didn’t reproduce

We tried a larger enclosed space that couldn’t be moved. The problem there was they quickly ate all the grass and the bottom of the cage turned to mud in the winter.

Draft Horses


The data of Pimentel and Pimentel (2008) suggest that energy use efficiency of draft animals is much higher than that of tractors. For our efforts in sustainable (energy efficient) agriculture, we tried using draft horses.

In 2001, our neighbor gave us a quarter horse mare. Sally was quite lonely and often ran away until Thor, a Belgian stallion, appeared one day in our pasture. Eleven months later, Marlon was born, and soon after that, Dookie arrived. They had their mother’s intelligence, and their father’s strength.

Thor (left) and Sally (right)

We learned to train draft horses at a farm in North Georgia.

Then we applied the lessons to Marlon and Dookie.

Our conclusion was that from the perspective of the farm system, draft horses may be more energy efficient than tractors, but from the perspective of humans, they are much more energy consuming. Now we just use them for hayrides at parties.

Poultry - Pasturized Chickens

We experimented with movable cages in pastures so that the poultry could eat the insects that invaded the soil after the cattle were moved. Although it was a lot of work, the baby chicks did well. However, it did not work for mature chickens in yards without a screen over the top. Hawks swooped in, and small mammals entered under the fence and beheaded the chickens. For pasteurized chickens, a system is needed where the chickens can safely retreat, such as that built by neighbors.


Mobile chicken coop and electric fence

Poultry - Duck Production and Nutrient Recycling

The objective of this project is to establish a duck production system that efficiently recycles nutrients. We have established a 10,000 square foot grazing yard for our ducks (Fig. 1). Within this yard, we have excavated two ponds, each about 25 feet on a side. The project begins with the ducks swimming in pond A (Fig. 2), and water hyacinth floating in pond B. The ducks defecate in pond A and enrich the nutrient content of the water. Once the hyacinth has spread in pond B, the ducks are moved there and several hyacinth plants are moved to A. The nutrients dissolved in pond A nourish the newly established plants. Once pond A is partially filled with hyacinth, the ducks are switched back.


Fig. 1 - Duck Pasture


Fig. 2 - Duck Pond


We supplement feed for the ducks with corn grown on the farm.  The entire cobs are fed through our chipper and the result is scratch through which the duck can pick.

Our biggest problem has been hawks and owls that swoop down and grab a duck dinner.  We have installed bird netting above the Duck pasture.

We started out duck production project with about 7 different varieties. The most successful was a cross between the black Cayuga and the Swedish blue (gray with a white chest).  We call the hybrids “Spring Valley Ecoducks”.  They are black with a white chest.

Spring Valley Ecoduck

Other Conservation Measures

Water Harvesting

Water harvesting refers to collecting and storing rainwater to be used for irrigating crops. The topography at Spring Valley Ecofarms lends itself to this practice. There is a 70 foot difference in elevation between our vegetable beds and the high point of the farm.

During heavy rains, water pours down the dirt road from the high point. We built a diversion dam that diverts water from the road into a ditch that leads to a collection pond. Water is siphoned out of the pond and into a drip irrigation system in the vegetable gardens below.


Drainage ditch and irrigation pond

Down slope edge of pond and siphon leading to drip irrigation system

Erosion Control

Sediment fences are fine plastic mesh used to control erosion at construction sites. They do not work well, because the mesh becomes clogged and soil then builds up and spills over the top of the mesh. At Spring Valley Ecofarms, we set up a series of 16 micro-watersheds to test the effectiveness of alternative approaches to erosion control. The most effective treatment to filter out sediment was a “sock” of fine mesh filled with compost.

The rain machine that delivers a set rate of rainfall over each of the micro-watersheds.  In each watershed, the erosion control devices are located just above the weir and tubes leading to collection bottles are just below the weir.

Forest Management


Natural forests usually consist of many tree species of all age classes.  I ask my students, “Why so many species?  Wouldn’t one expect that on a particular soil type with a particular climate, there would be just one species, the species that was best adapted to that environment?” The reason is, each species exploits a different niche. Some species do well as canopy species, others in the understory. Some species do well during wet years, others during dry years.  Some species have deep roots that capture deep ground water, others have shallow roots that intercept nutrients leached from the leaf litter.  Each species has different nutrient requirements.  Each species interacts differently with the insects, birds, and mammals in the forest.  Some species grow quickly, and invade openings in the forest.  Other species grow slowly, and eventually shade out the rapid growers. As a result, trees in a natural forest exploit more efficiently the environmental resources.

In contrast to natural forests, most forest plantations are monocultures. All the trees are of the same species and of the same age. From an ecological point of view, even-aged monocultures are undesirable. They use environmental resources inefficiently. The canopy of all the individuals has the same shape and is at the same height, resulting in competition for light. The roots are all at the same depth, competing with each other at the same time for water. All the individuals have the same nutrient requirements, with the result that some nutrients in the soil are scarce, while others are underutilized. 

Given the ecological superiority of uneven-aged, mixed species forests, why do many landowners plant even-aged monocultures? Because it is easier and cheaper to plant and harvest a plantation of one species than a forest of many species. However, there may be combinations of species that use environmental resources efficiently, and at the same time can be planted and economically utilized as efficiently as when in a monoculture. One of the projects at Spring Valley Ecofarms has been to evaluate various combinations of plantation species.  Fast growing species such as loblolly pine (Pinus taeda) , princess tree (Paulownia  fortunei)  and tulip poplar (Liriodendron tulipfera) with slow growing species such as oaks, ash, and hickory.  When a fast growing species such as princess tree is interplanted with oaks, the princess reaches marketable size in 12-15 years, while the oak remains small, but develops a strong root system.  A harvest of the princess trees acts as a release for the oaks, which then increase height growth.  After the harvest, the princess tree sends up sprouts that can reach 15 feet in one growing season.  The best sprout is selected and allowed to shoot up toward the canopy. If the canopy of oaks has not closed, a second harvest of princess trees is possible.

Inter planting of princess trees (marked with yellow ribbons) and oaks. Bark damage is due to deer grazing. Princess trees are in a second rotation.

An Alternative to Pine


In the 1800s, seed pods of the tree species Paulownia tomentosa were used as packing material for chinaware shipped from China to the U.S. The seeds scattered, and now this “princess tree” is considered an invasive, because it is often found growing in bare soil. Paulownia is an important wood species in Japan. During World War II, Japanese “Zero” airplanes were made of Paulownia, because its light but strong wood resulted in aircraft that were faster than U.S.’ aluminum planes. Today, they use it for furniture.

American foresters don’t like Paulownia tomentosa because its trunk often is not straight. There is another species of Paulownia however, Paulownia fortunei that produces a nice straight trunk. In the 1980s, Spring Valley Ecofarms facilitated a seed exchange program between Hunan Forestry University in China and Georgia Botanical Garden that resulted in Paulownia fortunei being established in both the Botanical Garden and at Spring Valley Ecofarms.

Paulownia has a big advantage over pine as a fast growing tree, in that it does not have to be replanted after a first rotation. Several sprouts arise after a tree is cut, and all that needs to be done is select the best sprout and cut the rest. Because the root system is already established, the sprout can grow 15 feet its first year. In contrast, to get a second rotation of pine in the Georgia Piedmont, the site must be bulldozed and mineral soil exposed before the pine seedlings are planted.

Paulownia fortunei at Spring Valley Ecofarms. The shrub beneath it with the burgandy flowers is Loropetalum chinense, also brought from China.

Growth rings of Paulownia tomentosa from a trunk originating from a sprout. Ruler is calibrated in inches.

Succession and Forest Management

In the mid-20th century, millions of acres  of cotton farms in the Georgia Piedmont  were abandoned.  Loblolly and short-leafed pine seeded in naturally over much of the old cotton fields.  Within 40 or so years, the pine gained economic value, and many land owners contracted with logging companies to log their land.  Usually the land owner wished to establish a plantation of pine on the logged over land.  There was a problem however, in that hardwood species such as oak and hickory had become established under the pine.  This is the natural order of secondary plant succession in the Piedmont.  In order to establish a pine plantation, the hardwoods had to be cleared out, usually with a root rake attached to a bulldozer, destroying soil structure and causing erosion.

Following a typical logging operation in the Piedmont, a bulldozer is clearing away debris to expose mineral soil in preparation for pine seedlings

By the first decade of the 21st century, most of the pines on Spring Valley Ecofarm were 60 or more years old, and some were beginning to be infested with the pine bark beetle. We contracted with a logging company to harvest them, but with the stipulation that they were to be careful not to damage the oak and hickory saplings that had established beneath the pine. They did what is called a selective harvest, using a feller buncher that slices a tree at its base without knocking it over and in an upright position, carries it to a loading platform. Most of the hardwood understory is left undamaged. What was once a pine forest became an oak-hickory forest.

A feller buncher at Spring Valley Ecofarms

Conserving BioDiversity

Energy saving in agricultural systems is achieved by substituting the free services of nature for energy subsidies such as fertilizers derived from petroleum.  Perhaps the most important measure that farmers can carry out is to preserve at least some of the farm in a natural area, where organisms that provide the free services of nature can be conserved.  Ecoagriculture is agriculture that strives to incorporate nature into farm systems, as we try to do at Spring Valley Ecofarms.

Restoring the Piedmont Prairie

Before colonists first settled  Georgia, the vast area between the Appalachian Mountains and the Coastal Plain was covered by an ecosystem type called the “Piedmont Prairie”.  It consisted of groves of oak and hickory trees surrounded by open prairies of native grasses where Indians hunted elk and bison that fed upon the grasses.  The Indians periodically burned the prairie to prevent invasion by woody species, and to remove the dead, dry grasses so that fresh new grass would grow unimpeded.

Until I acquired Spring Valley Ecofarms, most of the open areas were cultivated for wheat and sorghum.  I allowed most of the fields to fallow.  The first year, annual plants such as ragweed and sickle pod invaded, but after a few years, native grasses took over.  Soon, most of the old fields were covered with broom sedge (Andropogon virginicus), little blue stem (Schizachyrium scoparium), and occasionally big blustem (Andropogon gerardi) and Indian grass (Sorghastrum nutans).  Fields of native grasses waving in the wind were a beautiful site, and I tried to maintain the grassland by annual burning.

The ideal time for burning is in the winter months after a storm front moves through, wetting the soil so the fire can be controlled.   The first day after the front, the wind is too high. By the second day, the wind has died down, and the time is perfect for a burn.  A “drip torch” that dribbles a mixture of diesel and gasoline is used to set the burn.  The major problem was scheduling the burn with the Georgia Forestry Commission, required to be present with a pumper truck at the burn.  Schedules are made weeks in advance, and as a result, it was always unlikely that the scheduled day would be appropriate for the burn.   A second problem was the invasion of fescue,  a highly aggressive grass favored by cattle ranchers in the region. It remains green all winter, and so will not burn. Gradually it took over the fields and pastures where I keep my horses.  Ironically, the horses do not like it, and they eat the annual grasses down before they will touch it.   To restore the native grasses, I tried plowing and rototilling part of a pasture and broadcasting seeds of bluestem and Indian grass.  It took several years for the grasses to establish, but we made a mistake when we allowed the horses to graze them down to the ground.  Indians avoided this problem by continually herding the elk and bison to new grazing areas.

By 2011, only a small patch of broom sedge was left at Spring Valley Ecofarms

Old Growth Oak Forest


The family that originally owned what is now Spring Valley Ecofarms maintained about three acres of oak-hickory forest in back of the farmhouse, presumably as a source of firewood. However, soil in the grove was never cultivated. When we obtained the farm, the stand was impenetrably covered with privet, perhaps the most dangerous invasive species in the Piedmont. While the mature trees, some of which were 150 years old, were in good condition, there was no reproduction in the understory, due to the competition from the privet. We cleared the privet, first by cutting it, and then treating the sprouts with herbicide. The stand now has a healthy crop of oak and hickory seedlings and saplings.

Oak hickory stand at Spring Valley Ecofarms



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