Farmscaping to handle water also boosts curb appeal
Riverhill Farm in the Sierra Mountains near Nevada City, Calif., gets 50 inches of rain during the rainy season, and as much as 100 inches in an especially wet year, says Alan Haight, who’s owned the farm with his wife, Jo McProud, since 2001. Soil erosion and runoff laced with soilborne chemicals and nutrients could be major problems. Instead, there’s little erosion, and water leaves the farm cleaner than when it arrived.
“We have to be able to grow food in order to survive,” Haight says, “but we don’t have to, as part of that, harm the environment. One of the things I hope is that by farming this particular piece of land we can show that agricultural areas don’t necessarily have to contribute to the same kinds of problems that urban and developed areas do.”
He sees the farm as a small-scale watershed. While it’s on relatively level terrain, the north-facing slope drops 1,500 feet to the Yuba River, half a mile away. Runoff from the more gentle south-facing slope flows through a low-lying area of the farm into Rush Creek, which joins the South Fork of the Yuba River.
“The main contribution of the farm as a natural landscape is the low-lying wetland area,” Haight says. A former landscape contractor, he and McProud, a landscape architect, are using cover cropping, hedgerows and swales to reduce the amount of runoff and sediment leaving the farm.
The 20-acre farm has sandy loam soils 18 to 24 inches deep and clay subsoil. They’re using just 5 acres on the south-facing slope to grow more than 50 organic crops, including pears, tomatoes, strawberries, peppers, bulbing fennel and culinary herbs. They sell their produce within 10 miles of the farm, through community supported agriculture (CSA), to restaurants and a locally owned grocery store, at farmers’ markets, and their farmstand.
Haight has received grants from the Western Region Sustainable Agriculture Research and Education (WSARE) program of the USDA for a project that began in 2006 to conduct water sampling. This project is to determine if nutrients and/or sediment were being lost from the farm during storm events.
In 2008, he received a five-year cost-sharing grant from the USDA, which will allow him to observe the paths that the runoff takes during these storm events, create swales, and plant up to 3,000 linear feet of hedgerows where they’ll be most effective. It also will go toward removing non-native vegetation.
Although organic agriculture has a limited impact on the environment, disturbing the soil and leaving it bare can lead to erosion during irrigation or rain events, and the sediment can have major impacts on water quality downstream, he says. They use drip irrigation for more than 90 percent of their crops so there’s no irrigation runoff. In the fall, they seed the 5 acres to cover crops, typically rye and vetch, except for an area that’s planted with garlic, shallots and onions.
Plantings, whether hedgerows or cover crops, can work in a number of ways. Plant roots stabilize the soil, and plants trap the sediment in runoff, slow the movement of the water, and make the soil more permeable. This allows water to filter into the ground and recharge the groundwater instead of run off.
Hedgerows and swales
In 2008, Haight and McProud began planting hedgerows, or vegetative buffer strips (VBSs), in all the growing areas. Hedgerows are a key element in the battle against runoff, but most growers plant them to attract and provide habitat for beneficial insects.
As insectaries, hedgerows reduce the need for chemical pest controls, as they shelter insects such as parasitic wasps, lacewings and ladybugs, which prey on aphids, caterpillars and other insect pests. Many beneficials spend part of their life cycle eating only nectar and pollen. Planting species that bloom successively and have many small flowers, such as fennel, clover, yarrow, thyme and rosemary, provide both through the seasons.
“We have a great mix of species of plants so that through much of the year something will be in bloom,” he says. They’re all natives, including California bay trees, toyon, Coeanothus (California lilac), Romneya coulteri (Matilija poppy), coffee berry and yarrow.
As barriers, hedgerows prevent runoff and sediment from entering waterways. According to the Minnesota Department of Natural Resources Web site, they can intercept or remove 50 percent or more of nutrients and pesticides in runoff, 60 percent or more of some pathogens, and 75 percent or more of sediment. Their effectiveness depends on a number of elements, including their width and the species that are planted, the type of soil, the slope of the land, the volume of stormwater, and the paths runoff takes.
The USDA (through the NRCS) requires hedgerows to be at least 15 feet wide, planted to perennial shrubs and trees. Deep-rooted grasses and native plants are especially effective for controlling erosion.
Their location is crucial. The first hedgerows at Riverhill Farm were in the growing areas to serve as both insectaries and backup in case the cover crop is poor one year, Haight says. They’re working on the perimeter hedgerows now. They’re mostly following the fence line, where they already have about a mile of fence to keep deer and rabbits out of the fields, so they don’t have to take land out of production. However, they’re also creating some natural areas to plant hedgerows, and this does entail sacrificing some productive land.
“The location of some of these hedgerows is being planted to dovetail with our own observations about the paths water takes during storm events in the winter,” he says. “By planting permanent hedgerows in these areas where water concentration and movement occurs, we assist in slowing the water down and trapping sediment which might otherwise leave the farm.”
Hedgerows along waterways, or riparian buffers, stabilize streambanks and shorelines as well as provide habitat for beneficial insects, and slow runoff and allow it to filter into the soil. An EPA study found that riparian buffers are effective at reducing nitrogen levels in groundwater and streams, and the wider the buffer, the greater its effectiveness. A general rule is to plant them 50 to 200 feet wide on each side of the waterway, but many state and local governments have their own regulations.
Hedgerows require little maintenance. They need to be weeded and also graded occasionally to remove sediment buildup.
A conflict has cropped up as a result of some food contamination problems in the last years, Haight says. Many processors and handlers who receive food under contract require growers to remove habitat, which includes hedgerows. “It isn’t very good science, as most of the contamination has been attributed to human or livestock waste.”
He and McProud are also creating shallow swales in the south-facing slope to divert runoff from the growing areas and guide it to a low-lying area of the farm, which is planted in native grass. The swales increase the filtration of stormwater that would otherwise leave the farm and reduce the loss of sediment.
”There are many small farms,” he says. “The same thing can be done on a large scale with a larger impact.”
WSARE Water Sampling Project
The funding allowed Haight to take water samples and submit them to a local laboratory for analysis. “Analysis is quite expensive,” he says. “It would not have been possible for me to do it without the funding support.”
During storm events when there was visible runoff, he took a 1-liter sample from each of six locations on the farm. Two locations were above the farm, just before runoff reached the farm. Another, Location Number 6, was just below the farm, at the discharge end of a culvert at the property line. It’s fair to assume that this location represents the net effect of the farm, he says.
The samples were analyzed for nitrogen, phosphorus and total suspended solids (a measure of sediment). The results were favorable, and, in fact, compared with samples taken from one of the sites above the farm, which is adjacent to a paved road and a dirt road, there was actually an improvement in the quality of the water leaving the farm at Location Number 6.
“This shows the potential for farms to be an integral part of the landscape instead of a distant part,” he says. “What I’d like to see us do is go back to an earlier model, of an urban core surrounded by a satellite of very productive landscape, producing food of all kinds—and that by maintaining a patchwork of development and farmland, we can actually improve things for ourselves and the environment.”
The author is a freelance writer based in Altadena, Calif.