건조농법

Overview

Dry farming is not to be confused with rainfed agriculture. Rainfed agriculture refers to crop production that occurs during a rainy season. Dry farming, on the other hand, refers to crop production during a dry season, utilizing the residual moisture in the soil from the rainy season, usually in a region that receives 20” or more of annual rainfall. Dry farming works to conserve soil moisture during long dry periods primarily through a system of tillage, surface protection, and the use of drought-resistant varieties.

Dry farming has a very long history of use. Particularly in the Mediterranean region, crops such as olives and grapes have been dry farmed for thousands of years. Even today, vast swaths of Spain (e.g. Rioja and Andalucia), Greece, France, and Italy dry farm these crops, and in some regions of Europe it is illegal to irrigate wine grapes during the growing season, under the contention that the water will dilute the quality of the grapes.

The production of some of the finest wines and olive oils in the world is accomplished with dry-farmed fruit. The famous California wines that won the 1976 Paris Wine Tasting were all dry farmed. Today, California has dry-farmed vineyards all up and down the coast, from Mendocino in the north, Sonoma, Napa (estimated 1,000 acres), to San Benito, San Luis Obispo, and Santa Barbara on the central and south coast. There are a few old dry-farmed vineyards remaining in Lodi and the Sierra foothills, particularly Amador County. In addition to wine grapes and olives, a wide range of crops including tomatoes, pumpkins, watermelons, cantaloupes, winter squash, garbanzos, apricots, apples, grains, and potatoes are at times dry farmed in California.

Dry farming is not a yield maximization strategy; rather it allows nature to dictate the true sustainability of agricultural production in a region. David Little, a Sonoma vegetable grower who says he at times gets only a quarter of the yield of his competitors, describes dry farming as “a soil tillage technique, the art of working the soil; starting as early as possible when there is a lot of moisture in the soil, working the ground, creating a sponge-like environment so that the water comes from down below, up into the sponge. You press it down with a roller or some other implement to seal the top…so the water can’t evaporate and escape out.”

Dry farming is more than just the absence of irrigation. In the following example of wine grapes, there are five key elements:

• • The soil must be appropriate, with good water holding characteristics.
• • Grape vines must be spaced sufficiently to allow the plant to obtain the moisture it needs from the soil. In practice we have found that this varies from 32 to 120 square feet, which may in fact depend on the soil, rainfall, and altitude.
• • Vines must be planted on a rootstock that will seek the moisture down in the soil. Most dry farmers agree that St. George rootstock is best at this, although Frank Leeds reports that he has successfully dry farmed grapes on SO-4 and 110-R rootstocks. Vines are often given some water during the first season or two.
• • Vineyards tend to be cultivated as soon as the rains stop, in order to trap the moisture in the soil by creating a “dust mulch.” The word “dust” is really a misnomer, as true dust is undesirable and would just blow away. The goal is a 3-4” blanket of dry, even soil that prevents the moisture from escaping. Some growers emphasize the importance of disking the entire vineyard in a one-week window after the rains stop, which might limit the scale of any one enterprise. Others have achieved success mowing a permanent cover that was cultivated about every 6 years. one grower cultivates alternate rows for 3 years and then switches the cultivated and permanent cover rows, subsoiling the rows that were in permanent cover.
• • Vineyards are usually cultivated during the season in order to bring moisture to the plants, or rather to allow the plants to absorb the moisture and nutrients from the soil. Most farmers utilize a harrow. Though now controversial among soil scientists, this is almost a religious belief among dry farmers, and beyond the initial working of the vineyard to trap the moisture, the number of cultivations can range from once a season to once a week depending on the age of the vines, the variety, and the soil. Frank Leeds—who cultivates his mature vineyards every month—recommends the following fable from Aesop:

The Farmer and His Sons
A father, being on the point of death, wished to be sure that his sons would give the same attention to his farm as he himself had given it. He called them to his bedside and said, “My sons, there is a great treasure hid in one of my vineyards.” The sons, after his death, took their spades and mattocks and carefully dug over every portion of their land. They found no treasure, but the vines repaid their labor by an extraordinary and superabundant crop.

Obstacles

Because dry farming in California used to be a widespread practice, we know that its expansion is feasible. When planting a new vineyard or orchard in an area with sufficient rainfall, it is always an option. However, in the case of permanent crops, there are a number of obstacles to converting back, as described below.

• • In many cases, vineyards or orchards are planted too close together to simply stop irrigating them. Dry-farmed vineyards require a minimum of 50 square feet spacing for the vines, and probably more on hillsides. Wider spacing of plants is required on almost all crops grown this way.
• • Vineyards planted on riparian rootstock and shallowly irrigated with drip systems for years may have such shallow root systems that it would be difficult or impossible to convert. However, Frank Leeds of Frog’s Leap Winery says he has done just that in several cases in Napa.
• • Yield loss in dry farmed crops can be significant. Dry farmed red grapes farmed in the traditional manner with 9’x9’ or 10’x10’ spacing may yield as little as 1-3 tons per acre, although this is often on hillsides with shallow soils. However, in the Napa Valley, Frank Leeds says that he has to thin his more intensively dry farmed grapes back to 4 tons per acre, a normal yield for high-end wine. A number of growers report that dry-farmed white wine grapes planted in river bottom land produce very vigorous vines and high yields.
• • Quality of product and market conditions may not allow an economic return to the lower yields in many cases. In Napa, if a dry-farmed Cabernet Sauvignon vineyard gets $4,000 a ton, that is a very different outcome than the less than $500 a ton that the grapes might typically fetch in Lodi. While dry farming is physically feasible in Lodi, the market forces may not make it worthwhile unless dry-farmed Lodi grapes commanded a much higher price.
• • The same economic problem exists with dry-farmed fruit. Although such fruit is sweeter, denser, and stores better, it is also smaller, and the commercial fruit industry has spent many decades developing standards for large, blemish-free fruit that depend on significant application of chemicals, fertilizers, and water. Supermarkets demand large fruit because they sell it by the pound and they want to force the customer to buy as much as possible. It would take a significant marketing effort to create a price premium for dry-farmed fruit that could balance out the yield loss.
• • Dry-farmed orchards and vineyards come into production more slowly. It may take as long as five years for a dry-farmed vineyard to start producing.
• • Farming on hillsides always presents the problem of soil erosion. Dry farming techniques usually involve a significant amount of cultivation, often in the spring when erosion could be exacerbated. The repeated cultivation used in most dry farmed vineyards will cause nitrous oxide to be emitted if chemical fertilizers are used. Nitrous oxide is a much more potent greenhouse gas than carbon dioxide. The use of compost and other organic fertilizers appears to reduce this problem.
• • Finally, many agricultural areas of California are home to desert conditions with insufficient rainfall to pursue dry farming techniques. This is particularly true of the southern San Joaquin Valley. A place like Bakersfield averages only 6” of rain a year.

While dry farming is not for every grower or every region of California, it is a promising system of crop management that offers greater crop security in times of uncertain water supply and can offer a higher-quality product.

Water Savings

There is a lack of quantitative research documenting the extent of dry farming in California and its associated water savings. However, growers employing dry farming report significant water savings, not surprising given that irrigation is typically eliminated altogether.

As noted in the Frog’s Leap case study below, Frank Leeds estimates that his dry-farmed vineyards save a minimum of 16,000 gallons/acre compared to growers who irrigate lightly in Napa. Some vineyards use significantly more water. on Leeds’ 200 acres, he is saving a total of 10 acre-feet. If applied to 40,000 acres of vineyards in Napa, the water savings would translate to at least 2,000 acre-feet.

Jim Leap, when he was at the UC Santa Cruz student farm, calculated that he saved one acre-foot of water on each acre of dry farmed tomatoes compared to normal production in that region.

The UC Davis cost of production studies of typical California crops project the following volumes of irrigation water applied to the crop during a growing season:

• • 2-3 feet (2-3 acre-feet per acre) for olives in the Sacramento valley
• • 2 feet for potatoes in the Klamath basin
• • 3 feet for bearing apples in the Sierra Foothills
• • 30” for bearing pears in Lake/Mendocino area
• • 3 feet for mature green fresh market tomatoes in the San Joaquin Valley

As we face water cutbacks in the future, these generous estimates may become a thing of the past. Obviously growers work to maximize yields to the extent possible in their given conditions, but the current and future constraints growers in many regions of the state are facing where water supply is concerned may be sufficient motivation to explore alternate paths such as dry farming.

Applications

In addition to grapes, we have found that tomatoes, pumpkins, watermelons, cantaloupes, winter squash, olives, garbanzos, apricots, apples, various grains, and potatoes are all crops that are successfully dry farmed in California. For example, apples were traditionally dry farmed in western Sonoma County. While the fruit size was smaller, the yields were good and most of the fruit went for processing where size is unimportant. There are probably many more such examples. See the case studies section below for some examples of growers that dry farm such crops in California.

There are a variety of traditional vineyards and orchards along the California coast and in the Sierra foothills that have never been irrigated. “Old vine zinfandel” often refers to a dry-farmed vineyard that may be more than 75 years old. For example, Benito Duce has dry farmed in Paso Robles since 1925, with his Zinfandel mostly going to Ridge Vineyards. Bogle Zinfandel uses old-vine dry-farmed fruit from Lodi and Amador County. Fetzer and their Bonterra label use some dry-farmed fruit in Mendocino. Dr. Steve Gliessman (Condor’s Hope)—and a professor of agroecology at UC Santa Cruz—dry farms his vines and olives in Santa Barbara. The Bucklin Old Hill vineyard in Sonoma Valley is more than 125 years old, with the fruit going to Ravenswood and Bucklin wines. Kunde in the same area has a “century” vineyard.

A number of farmers in the premium wine-growing regions have developed and expanded the practice, including Frog’s Leap and Turley in Napa. Many practitioners of dry farming maintain that all premium vineyards in the coastal valleys could be converted back to the practice.

Sufficient rainfall is required, probably in the range of 15-20” per year, although Steve Gliessman believes that it can be done with as little as 10-12”. Even this smaller amount would exclude most of the southern San Joaquin Valley between Fresno (11”) and Bakersfield (6”).

Dry-farming requires not only sufficient rainfall but also soils capable of retaining moisture, so sandy soils or heavily fractured soils are inappropriate, many of the same considerations as with siting a pond.

Additional Benefits

• • The “dust mulch” (i.e., the dry layer of soil that is cultivated to trap moisture) is dry enough that few weeds grow, so herbicides are unnecessary, or, for organic farmers, little weeding is required.
• • Less water used on crops will have positive impacts on water quality and in-stream flows.
• • The energy used to transport and pump irrigation water is eliminated.
• • Establishment and maintenance of drip irrigation systems are eliminated.
• • Better tasting, more densely nutritious products.

Resources

Videos

A Return to Dry Farming, a video by Kate Wilson of Russian Riverkeeper

Dry Farming on the Cirone Farm, by Working for Green
Mike Cirone has not irrigated a single one of the fruit trees on the Cirone Farm for about fifteen years! So how is it that returning customers are still flocking to his stand at the local farmer’s market? Well, for the outstanding quality and flavor of his fruits of course! The Cirone’s Pink Lady apples, Fuji apples, sapotes, peaches and apricots are all products of the sustainable “dry farming” technique.

Books

Dryland Farming: Crops and Techniques For Arid Regions, by Randy Creswell and Dr. Franklin W. Martin
A concise overview of farming in arid regions. Includes a detailed description of dry farming techniques and practices.

Dry-Farming: Its Principles and Practice, by William MacDonald
This is a fascinating 1909 text about dry farming including information on the history of dry farming, conservation of soil moisture, rainfall and evaporation, tillage and crops. This free online version of the book (155 MB) is from The Internet Archive digital library.

Arid Agriculture: A Handbook for the Western Farmer and Stockman, by Burt C. Buffum
This is a 1909 text about farming in an arid climate with information about dry farming and moisture conservation and management techniques.
This free online version of the book (47 MB) is from The Internet Archive digital library.

Dry-Farming: A System of Agriculture for Countries Under a Low Rainfall, by John A. Widtsoe
This is a 1911 text about dry farming including information on dry farming conditions, soils, root systems, soil water storage, evaporation & transpiration, crops, and cultivation implements. This free online version of the book (53 mb) is from The Internet Archive digital library.

Agroecology: The Ecology of Sustainable Food Systems, Second Edition, by Steven R. Gliessman 
Covers dry farming and important information about the farm water environment. Available from Amazon for $63.89 as of Dec. 2011.

Articles

Turning water into wine: to water grapevines or not—the roots of the wine industry’s next great controversy, by Alice Feiring
A June 2007 San Francisco Chronicle article on irrigating wine grapes.

Taming the Tap, by Matthew E. Green
A March 2009 San Francisco Chronicle article on dry farming in California.

Back to the Future: dry farming, by Glenn T. McGourty
A February 2010 Wines and Vines article on dry farming wine grapes, by a Mendocino County farm advisor.

In Napa, a new path to using less water, by Jon Bonne.
A March 2010 San Francisco Chronicle article on dry farmed grapes in Napa by the newspaper’s wine editor.

Dry Farming: Old Techniques for a Sustainable Future, by Rachel Raphael
A Summer 2010 Edible Marin and Wine Country article. Includes discussions with John Williams and David Little.

How Dry I Am, by Alastair Bland
A May 2011 article in The Bohemian on dry farmed vineyards and more in Sonoma County.

A Field Guide to Sustainable and Delicious Dry Farmed Wines, by Alastair Bland
A June 2011 San Francisco Weekly article.

Dry Farming Vines, by Terry Harrison.
Prepared for the Eco-Winegrowing Symposium in Hopland, CA on July 20, 2011. Harrison, a former grape grower in Healdsburg, CA, discusses what he learned from CAFF’s dry farming field days with Frank Leeds, John Williams, Paul Bernier, Joe Votek, and Will Bucklin.

Case Studies on Dry Farmed Vineyards

Frog’s Leap Winery, Rutherford, CA

Frank Leeds’ and John Williams’ successful dry farmed vineyards in the Napa Valley.

The Poor Ranch, Hopland, CA

The Poor Ranch, run by John and Susan Poor in the hills above Hopland in Mendocino County, was homesteaded by the Poor family in 1888, and has expanded to over 1,000 acres. The Poors have 90 acres of wine grapes—80 are organic—including Zinfandel, Petite Syrah, Carignane, and Grenache. The Poors have always dry-farmed their grapes.

Case Studies on Other Dry Farmed Crops

Molino Creek Farm, Davenport, CA

Dry-farmed tomatoes were popularized by the Molino Creek Farm on the Santa Cruz coast at Davenport. As described on their website: “Critical to producing our best-tasting tomatoes is our method of dryland farming. We were pioneers in working out the means of growing tomatoes that are not irrigated at all. They survive by rooting themselves as deeply as possible into our rich clay soil and searching for moisture retained from the winter rains. Located on the Central Coast of California, we enjoy moderate summers in a microclimate of both sun and summer fog. With the combination of deep fertile soil and temperate weather, our tomatoes can produce the sweetest and most intense flavors.”

UC Santa Cruz Farm, Santa Cruz, CA

Jim Leap, the former farm manager at the UC Santa Cruz farm, had been teaching dry farming techniques that he learned from Molino Creek to his students for 20 years. He grows tomatoes, winter squash, dry beans, apples, and apricots. He transplants tomatoes in May after earlier trapping the moisture by tilling. Again, generous spacing is required, just as with perennial crops. He warns against heavily irrigating after transplanting, because you want the plant to drive its roots down into the soil

Little Organic Farm, Petaluma, CA

David Little dry farms potatoes, tomatoes, winter squash, onions, garlic, and other vegetables in Petaluma. He sells them to restaurants and at farmers markets. Potatoes have been dry farmed in Marin and Sonoma since the 1850s. Little says that he struggles with low yields (he estimates his yields at 25% of his competition) and the lack of a price premium for dry farmed crops.

Flatland Flower Farm, Sebastopol, CA

Dan Lehrer dry farms apples in Sebastopol, which he started doing by accident when his drip irrigation system broke down. He reports richer, crisper apples that ripen later and store longer.

Oh! Tommy Boy’s Organic Farm and Coastal Fog Organic Farm, Petaluma, CA

Oh! Tommy Boy and Coastal Fog dry farm 30 varieties of potatoes in Petaluma. They sell them at their farm stand, farmers’ markets, and to some stores and restaurants. The ranch has dry farmed potatoes since 1926, and their relatives have dry farmed potatoes since 1853 in the town of Bloomfield. Click here for a feature on Jim Morris and clan in Ag Alert.

Casey Hoppin, Knights Landing, CA

Casey Hoppin dry farms melons in Knights Landing, Yolo County. He says you have to have the right soil to make it work.

http://agwaterstewards.org/index.php/practices/dry_farming/#savings