OF Dec Jan 2020

Interior temperatures for compost cannot exceed 150 to 160 degrees F in order for
microbial activity to remain undisturbed (photos by K. Piper.)
Continued from Page 29
Grower Usage
Jean-Pierre Wolff, principal owner of
Wolff Vineyards in San Luis Obispo,
Calif., explained in a phone interview
his own usage of compost in his soils
and the benefits it has provided him.
“I’ve been applying compost postharvest
for 20 years and apply 1.5 tons per acre,”
Wolff said. “It takes several years for
compost effects to take place in terms
of mineralization. In my case, in the
first 10 years, I was mixing compost
with gypsum. Now, I’ve switched to
100% compost to give priority to the
carbon content. The benefit of the nitrogen
content is a slow leaching, which
has been a good approach for us in the
vineyard to have a slow and steady feed
of nutrients. It also increases microbial
activity due to the higher quality of
compost.”
Wolff switched to using Cal Poly’s compost
mix in recent years for multiple
reasons including its close proximity to
his vineyard.
“Years ago, I used dairy farm compost
from the Central Valley,” Wolff said.
“Because of the transportation costs, I
switched to green compost from Santa
Barbara county. Now, I use Cal Poly’s. I
switched to them because they’ve gone
through a lot of upgrades on their compost
equipment and they also offered
training classes. Close proximity was a
big part of the decision.”
Even though the use of compost has
been working out for Wolff’s vineyard
over the years, he made it a point to
note a couple of major tips when using
and buying compost.
“One area which I think can be problematic
because of climate change is
that it [compost] only works well with
areas of normal rainfall,” Wolff said. “I
proved this during the latest drought.
Utilizing drip irrigation just does
not have the same flushing affect for
nutrients into the soil as rain does. The
microbe activity of freshly applied compost
diminishes if this is the case.
“Not all composts are created equal,”
he continued. “The whole business
of it starts with the quality you get.
It sounds fundamental, but it’s key.
Always get compost from a reliable
source.”
Producing and using compost is a
complex process for both sides, and
patience is required. Producers have
to ensure that their final product is
up to par (i.e. good feedstock sources,
properly heat-treated, adequate nutrient
levels and absence of any harmful compounds)
and growers need to ensure
that they are buying from the right
source and utilizing good compost
practices themselves.
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30 Organic Farmer December/January 2020