University of Vermont Extension
Department of Plant and Soil Science
Fall News
Article
PREPARING GARDEN SOILS FOR SPRING
Dr. Leonard Perry, Extension Professor
University of Vermont
Fall is an excellent time to prepare garden soils for spring, for several
reasons. You usually have more time than in the busy
spring. One of my favorite reasons is that, being at the end of the
growing season, weeds don’t regrow! Often in the spring soils remain
too wet to “work” for long periods. Amendments added in fall have time
to incorporate before spring. Removing diseased plants in fall keeps
such diseases from overwintering in the soil, only to reemerge the following
growing season. Of course if you are planting fall crops such as
spinach, or garlic in fall for the following season, you’ll need to prepare
the soil first.
When removing old vegetation, whether vegetables or weeds, don’t put them in
the compost if they are diseased, have weed seeds, or thick stalks that are
difficult to decompose. Instead, bag such and take them to a recycle
center where they are equipped to deal with such. If weeds have gotten
away from you and gone to seed, try to carefully cut off the seeds first and
remove them so that they won’t disperse around the garden as you pull up
plants.
For perennial weeds, make sure to remove any roots, or they will regrow next
year. Tilling them in will only break up the roots into many more
pieces, multiplying your problem next season. For weeds with
wide-spreading root systems, such as some grasses, you may need to use a
synthetic or organic herbicide to kill them back.
If you can get the garden cleaned up by early fall, you can plant a cover
crop. This is simply a crop such as oats or clover that will protect
the soil from erosion, and add important organic matter when tilled in
later. If later, winter rye is about the only choice. If frosts
have begun, it is probably too late to establish a cover crop before winter.
Tilling the soil, once you’ve cleaned off any plant material, is generally
not a good idea unless you simply want to incorporate organic matter or the
site is new. Tilling actually destroys soil structure, and buries the
microorganisms that live in the top three inches or so of the soil, and
which are important for soil health. Tilling repeatedly also creates a
“hard pan” or fairly impervious, compacted layer at the depth of the tiller
tines—about 6 inches. Water and roots can’t penetrate such a hard pan
easily. Soils generally contain a lifetime supply of weed seeds
(unless harsh pre-emergent herbicides have been used). Tilling will
bring buried weed seeds to the surface where they can germinate.
Tilling of course creates bare soil, and this is not good for several
reasons. Nature doesn’t like bare soil, and wants something green
there. If you don’t have it covered nature will, in the form of
weeds. These blow in and germinate readily on bare soil. Bare
soils are exposed to the sun, which can vaporize and decrease soil nitrogen,
and kill off those important microorganisms near the soil surface.
Bare soil, also, is subject to erosion by wind and water.
Instead of tilling, loosen established soil beds simply by inserting a
garden fork every few inches and rocking it back and forth. Surface
cultivate for weeds around plants, and use mulches in rows. I like to
use several layers of newspaper, covered with weed-free straw, in
rows. Not only does this keep the weeds down, but provides a great
surface to walk on and kneel on when weeding. When incorporating
organic matter into the soil, use a garden “claw” tool to work it into the
surface. You might even set up such garden rows and paths in fall,
ready for spring.
Fall is a great time to test the soil, so you know what is needed (if
anything) when planting in spring. This is especially true for
lime—often needed to raise the soil pH or make it less acid. Most
forms (such as the common dolomitic lime) take some time to work, so adding
them in fall means the soil will be at the right pH (or soil acidity) by
spring.
You can contact your local Extension Service office for a soil test kit, or
find them at some full service garden stores. State universities do
the soil tests, and provide results tailored for your region.
Inexpensive home test kits can be purchased as well, although these are less
accurate, especially if they are old and the testing chemicals not fresh.
In addition to possible nutrients such as lime, fall is an excellent time to
add soil amendments such as the organic matter already mentioned. This
breaks down in soils, so you need to add it yearly. Organic matter
loosens heavy clay soils, helps sandy soils hold more water and nutrients,
and by attracting all those soil microorganisms makes soils healthier.
Compost is perhaps the most common amendment. Add an inch layer on
soils, and work in several inches using a garden fork, rake, or claw.
Add a bit more if a new site or poor soils (clay or sand). For 1000
square feet, for an inch layer of compost, you’ll need about three cubic
yards. You can buy this in bags but, for large amounts such as this,
check locally for bulk deliveries.
If a local compost product, make sure it is free of weed seeds. If it
hasn’t been produced properly (at high enough temperature or using livestock
manure which often contains hay seeds), you’ll fill your garden with all
manner of weeds. Test such products before applying, simply by putting
some in a pot, watering, placing in a warm spot and seeing what germinates
(hopefully nothing).
Other sources of organic matter include shredded leaves and dehydrated cow
manure, or bagged garden soils (good for raised beds and smaller areas)
containing compost. Don’t use fresh wood products, such as sawdust, as
they rob the soil of nitrogen as they break down.
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