The Rural Voice, 1979-05, Page 38Advice on Farming
Sewage sludge on the fields?
The disposal of human and animal
wastes is an expensive problem for society
but studies indicate that these wastes are
resources which can be put to good use if
managed properly. They contain nitrogen,
phosphorus, potassium, and other ele-
ments vital to plant growth. They can be
used in place of, or in conjunction with,
commercial fertilizers. Sewage sludge may
contain undesirable heavy metals, such as
cadmium and zinc, so it must be used
carefully. Generally, this problem does not
arise with manure.
Nitrogen in these wastes is especially
important because costly nitrogen fertilizer
must be applied yearly. Corn and grass
forage crops, the two major crops in
Ontario in acreage, require large quantities
of nitrogen. Ontario farmers spent $68
million on nitrogen fertilizer last year. The
corn crop accounted for nearly $30 million
of the total. These costs will continue to
increase as energy prices climb.
We know there is enough manure
nitrogen produced in Ontario annually to
supply the total nitrogen requirements of
the corn crop. Proper use of manure and
sludge, in place of commercial nitrogen
fertilizer, can save Ontario farmers a lot of
money, especially if they are raising
livestock. Making better use of these
by-products will also reduce the need for
nitrogen fertilizer, and conserve the high
amounts of energy involved in its produc-
tion.
The advantages of using manure and
sewage sludge as nutrient sources are
known to farmers. Many farmers are
already putting these materials to good use
on their fields—or think they are. However
most farmers applying manure or sludge
are not getting the full value of the
nitrogen it contains.
Research at the University of Guelph
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indicates that a considerable amount (from
one third to two thirds) of the available
nitrogen contained in manure and sludge
can be lost to the atmosphere instead of
entering the soil. This Toss, called volatil-
ization, is similar to the loss of water by
evaporation from a moist, bare soil.
A recent study by Beauchamp, Kidd and
Thurtell, Department of Land Resource
Science, Ontario Agricultural College,
measured the extent of volatilization, or
loss of nitrogen, one week after applying
sewage sludge to a field at the University
of Guelph, Elora Research Station. Re-
searchers measured concentrations of
ammonia (nitrogen) in the air above the
field before and after application of sludge.
The first experiment was conducted in
May, and repeated in October. Results
showed up to a thousandfold increase in
atmospheric ammonia after both May and
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THE RURAL VOICE/MAY 1979 PG. 37