By
Kimberly Warren
Managing Editor
Every day, all year long,
people are throwing away what could be of vital importance to growers.
In fall, leaves pile up in streets and yards waiting to be taken away.
In winter, old Christmas trees, holly and wreaths litter garbage cans.
In spring, people clean out gutters, ditches and yards to get ready
for the green summer grass. And every weekend in the summer, lawns
all over America fill with people pushing lawnmowers.
And all of these things, from the fall leaves to summertime grass
clippings could be something growers are looking for: a recipe for
soil health – all of them organic materials that can be mixed
together and composted to add nutrients and beneficial microorganisms
to soil.
“One of the best ways to have good quality, healthy soil, is
to amend the soil with compost,” said Matthew Ryan, research
technician with The Rodale Institute.
Dave Wilson, a research agronomist at The Rodale Institute, said there
are three main reasons someone would want to use compost: physical
benefits, nutrient benefits and biological benefits.
When putting synthetic fertilizers or dairy manure on soils, there
is heavy leaching, Wilson said. This leaching means that the nutrients
in the manure or fertilizer pass through the soil and past the root
zone, which does not benefit plants and may have negative environmental
impacts. With compost, Wilson said, the nutrients stay where they
are put and take a much longer time to leach out of the soil, thus
keeping those nutrients available to the plants for a longer period
of time. Besides this nutrient benefit, the physical benefit of compost
is that it has a greater water holding capacity.
“When you have a rainfall event and some of your water starts
to run across the top of the soil, by having compost and organic matter
in the soil act as a wick to pull water into the soil,” Wilson
said. “Second, once it’s in the soil, it acts as a sponge
to retain that water. In other words, your soils don’t dry out
as quickly.”
For this reason, Wilson and Ryan have seen greater yields in the organic
systems, compared with the conventional systems, in drought years.
Compost also contributes biological benefits. Not only are growers
introducing beneficial microorganisms with the compost, but they’re
also feeding soil microorganisms with the addition of organic matter,
Wilson said.
But just how can growers get started using composts?
Ryan said composts can be made of nearly any organic material –
from leaves to leftover food (vegetable) scraps from local school
cafeterias. But it’s important not to have any meat products
in compost because it could attract rodents, he said.
“And sometimes you have to watch out for grass clippings that
have had herbicides applied to them,” Ryan said. “There
have been some cases where clippings have herbicides residues on them
that don’t breakdown in the composting process, and the compost
made from these clippings inhibited the growth of plants.”
Much of the compost used at The Rodale Institute comes from municipalities.
Leaves are typically mixed with manure at a ratio of 4-to-1 for Rodale
compost piles, Ryan said. It takes just a little research and an open
mind to find good compost materials.
“With a little creativity and insight, you can usually find
materials to make good compost right under your nose,” Ryan
said.
Compost piles should sit anywhere from six months to two years before
they are suitable to use, Ryan said. For organic production, growers
turn their compost pile five times during a 15-day period once the
compost pile heats to 131° F. Compost made this way should be
ready to be used within one year. Compost that isn’t turned
should not be used until two years have passed.
“We (The Rodale Institute) have multiple composts going so every
year or every six months, there would be a mature pile of compost,”
Ryan said.
Regardless of what materials and composting methods are used, growers
should test their compost before using it to make sure it is mature.
And one way of doing this is with “the stink bag test,”
Ryan said. For the stink bag test, a grower would need to take a small
sample of the compost and put it in a plastic bag somewhere warm.
The bag should sit for about a week and when opened, it should smell
earthy. If the compost smells bad, Ryan said, it is not yet mature
enough to use. There are also other home test methods available, such
as the cress/cucumber germination test and the Solvita Compost Maturity
Test Kit, available at www.woodsend.org. Immature compost is fine
for early season field applications, but not for potting mixes or
potted plants.
Once the compost is mature, it can be applied directly to the soil
under the plants, or it can be worked into the soil. Another method
of composting is using compost tea. True to its name, this age-old
method often involves filling a large burlap bag with compost at a
ration of 1-to-5 (compost to water) and putting it in a water-filled
plastic garbage can. The tea will then steep, releasing the nutrients
from the compost into the water. Growers can then apply the tea by
spraying it on the leaves of the plants.
“You don’t get the physical benefits like the added organic
matter, but with the tea, you can apply it right to the leaves and
it will act as a foliar fertilizer – something you can’t
do with the physical solid compost,” Ryan said.
Researchers at The Rodale Institute are currently experimenting with
aerated compost tea, which is a little different and involves aerating
the solution. For more information about aerated compost tea, visit
the International Compost Tea Council’s Web site at www.intlctc.org.
For more information about compost or the compost tea trials at The
Rodale Institute, visit www.rodaleinstitute.org or www.newfarm.org.
To receive a fact sheet that answers 25 frequently-asked composting
questions and provides a resource list, write to infor@rodaleinst.org
or call (610) 683-1415.
