Vineyards apply custom blends of food-scrap compost
In the last 60 days modern compost facilities in
California have shipped 7,500 cubic yards (218 truckloads) of finished
compost made with food scraps collected from San Francisco and Oakland
restaurants to local vineyards.
The compost, made from a diverse feedstock of
kitchen trimmings and plate scrapings, returns nutrients to vineyards
and farms, stimulates microbial activity and improves soil structure.
Now growers are taking the additional step of
having the two Northern California compost facilities blend in extra
amendments such as rock phosphate, gypsum, lime and sulfate of potash.
“By applying compost blended with specific
amendments that lab tests of vineyard soils show are needed we can
tailor the compost to feed vineyards and farms nutrients they more
specifically require,” said William Brinton, who operates
Woods End Research, a soil and compost-testing lab, and advises
growers on compost recipes and soil requirements.
The two compost facilities, Jepson Prairie Organics
and South Valley Organics, make Four Course Compost from restaurant
food scraps, store additional amendments onsite and mix custom compost
blends to vineyard specifications.
Blending rock phosphate into compost, called “rock
composting,” is an extra step that most compost operations
will not take but is highly beneficial to growers, said soil scientist
Bob Shaffer, of Soil Culture Consulting in Glen Ellen, California.
The phosphate comes from a Florida mine. “It
is very high in quality, a pure source of phosphate particles,”
Shaffer said. Microorganisms and humic and folvic acids in the compost
“pre-digest” the phosphate; that action makes the essential
mineral more available to plant roots and increases nitrogen retained
in the compost, Shaffer said.
Adding phosphate also provides calcium, iron and
trace elements. “Plants respond to this very well,”
Every harvest removes nutrients from the soil.
Nutrient-rich compost returns nitrogen, phosphorus, potash and organic
matter to the soil, giving growers an alternative to chemical fertilizers.
The finished compost encourages leafy growth and
succulence, promotes a strong root system and builds disease resistance.
Blending in amendments at the compost facilities also saves growers
the time and expense of doing it in the field.
More than 100 vineyards and several organic farms
have applied truckloads of the rich soil amendment. Many are rushing
to apply the soil amendment before the winter rains begin.
The Organic Material Recovery Institute (OMRI)
of Eugene, Oregon has a process to approve specific natural amendments
based on review of the ingredients and the composting methods. OMRI
has approved Four Course for use on organically certified farms.
More than 2,000 restaurants in the San Francisco
area and thousands of city homes provide food scraps to the program.
Sunset Scavenger and by Golden Gate Disposal & Recycling, operating
companies of Norcal Waste Systems, Inc. collect 330 tons of compostable
material a day.
The scraps are transported to Jepson Prairie Organics
and South Valley Organics, compost facilities owned and operated
by San Francisco-based Norcal. Compost workers screen, grind, compost
and cure the material using modern composting equipment and techniques.
The end products include Four Course and associated blends of nutrient-rich,
finished compost favored by Northern California vineyards and organic
“This is our busiest time of year,”
said Robert Reed, spokesman for Jepson Prairie Organics and South
Valley Organics. “The growers want to get this compost on
their vineyards and fields now because the rain will carry the nutrients
into the soil to feed plant roots, and the compost will help soil