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.
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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.
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.
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.
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.
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.
Organic Fruit Orchards
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.
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.
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.
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.
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.
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.
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.
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.
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.
An Alternative to Pine
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.
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.
Old Growth Oak Forest