October 1, 1998
Forage Systems Update
Vol 7, No. 4
What about Dragging Pastures?
One of the questions that I commonly hear at
producer meetings is: "Does it do any good to drag
pastures?" My usual answer is the universal extension
answer for all questions, "It depends!" and that is
usually followed by my question, "What are you trying
to accomplish?" Someday when you have a lot of time
on you hands, think about all of the things you do during
a day and ask yourself what you are trying to accomplish
with each task. The results may be a little scary.
What are we trying to accomplish with dragging
pastures? The most common goal is to spread manure
piles to accelerate manure decomposition and enhance
nutrient cycling. Covering seed or disturbing a thatch
layer are other common objectives. Dispersing manure
piles may also lead to more uniform grazing. On some
farms dragging pastures is a tool to transfer funds to
dependent children in a tax deductible manner.
Does dragging to scatter manure piles actually
enhance nutrient cycling? For all practical purposes, no
research exists to answer this question. From high
school chemistry or building a campfire, we know
intuitively that as particle size decreases rate of reaction
increases. Thus, if manure piles are reduced to manure
fragments, they will decompose more quickly. The
smaller particles also have greater surface area contact
with the reactive surface (ie. the soil). I believe it is a
pretty safe assumption that nutrient cycling is
accelerated following dragging.
The next question is, is the rate of increase in
nutrient cycling economically meaningful? I really
haven't a clue whether it is or not. Some other aspects
of dragging pastures may have economic relevance. The
chain or flex type harrow is a very useful tool for
bringing overseeded legumes or grass into better contact
with the soil. The greater likelihood of the overseeded
crop establishing is probably worth the cost of dragging.
Manure dispersal comes as an added benefit.
Spotty grazing is very often the result of
livestock avoiding manure piles. Scattering those piles
can lead to more uniform regrowth and less selective
grazing. To completely avoid manure-induced spot
grazing is virtually impossible with any class of
livestock which are in a production mode. Dragging
pastures after every grazing period to avoid spot grazing
is probably not economically feasible.
Timing of dragging can be fairly critical.
Autumn dragging to break piles up going into the winter
can result in much more even growth on pastures which
do not receive nitrogen fertilizer. Nutrients contained in
the manure are likely to be back into the soil solution for
early spring growth if autumn harrowed. Manure piles
that have dried a few months tend to shatter and scatter
very nicely this time of the year. It also ensures that
legumes seeds contained in dung piles are more likely to
come into soil contact in the spring.
Spring harrowing can either accelerate or slow
pasture growth rate in the spring. Harrowing prior to or
at green-up frequently accelerates pasture growth by
disturbing the thatch layer and allowing the soil to warm
up more quickly. We have measured 3 to 5o F
differences in soil temperature in side by side harrowed
and unharrowed strips in early spring. But if harrowing
is delayed too long after early green-up, growth rate can
actually be slowed due to damage to tender young plant
growth. Delaying dragging too long in the spring can
also result in destroying legume seedling growing on
dung piles.
Some concern has been expressed that dragging
pastures may increase the likelihood of spreading infection
of intestinal parasites to grazing animals. While this may be
a concern in some environments, it is generally not
considered to be a problem in the Midwest and Upper South.
Manure in dragged pastures dries out very quickly during
most of the year (May to October) in Missouri. Exposing
more manure surface area to the sterilizing effects of solar
radiation kills most parasites. Simply drying the manure out
reduces the likelihood of some survival for some organisms.
In cooler, cloudy climates, parasite persistence is much more
of a problem. Parasite reinfection due to dragging is also
more likely to occur with horses than with cattle due to the
very severe overgrazing habits of set stocked horses.
We have kicked the piles around and thought about
some of the benefits of dragging pastures. It is very difficult
to say whether or not the benefits of dragging are worth the
cost of doing it. In terms of economic importance, I would
rate the benefits in the following order: reduce spot grazing
(enhanced utilization rate is the economic benefit); improve
seed/soil contact (the economic benefit is improved pasture
productivity; and accelerate manure decomposition (the
economic benefit is reduced fertilizer input)
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