After harvest, Will Bakx loads
trucks with compost and mulch for delivery to vineyards in Sonoma and Napa
counties. Bakx, a soil scientist for Sonoma Compost in Petaluma, CA, produces
high-quality compost from urban yard trimmings. Many vineyard managers who
apply compost and mulch after harvest are finding these products to be useful
components of their vineyard floor management program.
While some vineyard managers purchase
these soil amendments, others make their own compost from grape pomace. Either
way, compost and mulch are products that result from recycling materials that
might otherwise be wasted. As many communities collect yard trimmings at the
curb to reduce organic materials going to landfills, these materials are being
transformed into valuable soil amendments by producers such as Bakx. Growers
and researchers alike are discovering the benefits of these recycled soil
microbes in compost may help reduce phylloxera damage
Under the guidance of phylloxera
researcher Dr. Jeffrey Granett in the UC Davis Entomology Department, Ph.D.
candidate Don Lotter has been monitoring damage caused by phylloxera in organic
vineyards for two years. Indications are that vineyards using compost are
doing well if theyve been applying compost for at least four or five
years, according to Lotter.
Lotters research shows
significantly less root rot (11.8%) in organically managed phylloxerated
vineyards than on phylloxerated roots from conventionally managed vineyards
(27.1%). Each of the six organic and seven conventionally farmed vineyards that
were monitored have similar sand/silt/clay ratios. All of the vineyards showing
favorable results are using compost in combination with winter cover
Phylloxera feeding on the grape roots
make the grapevine vulnerable to infection by fungal pathogens, such as
Fusarium. However, in the organically managed vineyards, Lotter found a trend
toward higher populations of beneficial microorganisms that are antagonists to
Fusarium. These beneficial microbes include Trichoderma and Pseudomonas or
Pseudomonad bacteria. (Additional information on UC Davis phylloxera research
is available at http://entomology.ucdavis.edu/faculty
Compost has long been known for its
wealth of microbial activity. Beneficial microbes flourish during the aerobic
composting process, where oxygen is made available to the microbes either by
turning the heap, thereby increasing the porosity, or by pumping air through a
There is also a relationship between
phylloxera and soil type. According to the University of California Pest
Management Guidelines on Grape Phylloxera, Phylloxera prefers heavy, clay
soils, that are commonly found in the cooler grapegrowing regions of the state
such as Napa, Sonoma, Lake, Mendocino, and Monterey counties, as well as the
Sacramento Delta and the foothills. Compost is a good soil amendment for
improving soil structure and aeration of these heavy soils.
Compost is an investment in the
long term health of the soil and the plants, asserts Bakx.
soils, prepares ground for cover crops
John White of Pina Vineyard Management
is a strong advocate of compost. He has been using compost for a number of
years and purchases it from several different Napa Valley producers. We
apply compost before planting or within the first year to improve the heavy
valley soils and to build soil organic matter, says White. At an
application rate of 10 tons per acre, White is applying more compost than most
vineyard managers. However, the higher application rate may be necessary to
help loosen heavy soils.
Fetzer Vineyards (Hopland, CA) is a
subject of Lotters phylloxera study. However, when asked why he uses
compost, vineyard manager Tom Piper doesnt even mention phylloxera damage
control. He cites improved soil structure, the addition of potassium, and
beneficial microorganisms. In addition, Fetzer sows the seeds for its annual
cover crop onto a bed of recently applied compost with good results. Unlike
Pina Vineyards, Fetzer makes its own compost on-site.
We make about 200 tons of
compost every year from our pomace, explains Piper. We turn it with
a front-end loader, so we didnt need to invest in any special
equipment. Compost is applied at about one ton per acre to established
Fetzer vineyards and two tons per acre for new plantings.
Delicato Winery has been composting
grape pomace on-site for more than 15 years. Although Delicato originally
invested in large-scale composting equipment, such as a Scarab turner, and sold
compost to other growers, the winery now only makes enough for its own use,
selling the remaining pomace for animal feed.
Grape compost makes a great soil
amendment, says Bud Bradley, Delicatos director of grower
relations. It helps make the soil what I call healthy, improving
drainage, and water-holding capacity. Bradley touts the widely held view
that soils high in organic matter are not as attractive to nematodes. Delicato
vineyards receive an average of five tons per acre of compost each year over
130 acres. Lab analysis of the compost is a standard practice at Delicato.
Characteristics tested include nitrogen, phosphorus, and potassium (NPK), other
soil nutrients, and heavy metals.
contribute to healthier vines and increase yields
Andrew Hoxsey of Yount Mill Vineyards
is now in his third year of making compost for his organic vineyard with
restricted inputs. After experimenting with commercially produced compost, he
decided to try making his own custom blend. He now blends 40% pomace and 30%
turkey manure with 30% composted yard trimmings from a local commercial compost
Hoxsey is pleased with his blend and
finds that vines that were stressed in 1995 and 1996 now appear healthier.
The primary reason we use compost is to add organic matter and boost
microbiological activity, says Hoxsey. Three to four tons per acre of
compost is applied over the 600 acres of Yount Mill vineyards.