Soil Management Handbook - Ministry of Agriculture and Lands

"tie up" some soil nitrogen, although to a lesser
degree.
To overcome nitrogen deficiencies in soils amended
with woodwastes, a sufficient quantity of nitrogen, to
allow for decomposition, should be added to the
woodwaste before or during the application. Note
that still more nitrogen may be required for cultivated
crops. The rates suggested below are nitrogen
requirements for the woodwaste only and are
calculated to reduce the C:N ratio of the woodwaste
to 100:1 or less. An example of the amount of
nitrogen required to achieve a C:N of 100:1 or less is
as follows: for 10 cm (4 in) of sawdust, an equivalent
of 1000 m 3 /ha (536 yds 3 /acre), use 785 kg of N per
hectare (700 lbs of N per acre). This example is
based on Douglas fir sawdust at 270 kg/m 3 (16.9
lbs/ft 3 ) wet or 155 kg/m 3 (9.7 lbs/ft 3 ) dry. Typical
C:N's of Douglas fir is 471:1 for bark and 1268:1 for
wood.
4.5.1.3 Peat Moss
Peat moss or other types of organic soil material
provide a small quantity of plant nutrients, but their
greatest benefit comes from improving the
water-holding capacity of sandy soils and improving
the tilth of fine-textured soils. Abundant, economical
sources of peat moss for soil amendments are not
readily available for field scale agriculture. However,
in intensive horticulture markets, nursery and
greenhouse, supplies are available. In place of using
peat moss in field scale agriculture, products such as
composted animal manures may be more readily
available and also have the benefit of supplying some
plant nutrients.
4.5.1.4 Compost
Compost is made from organic materials such as crop
residues, clippings, leaves, small animal morts,
animal manures or woodwastes. Soil organisms
almost completely decompose the organic matter and
the end product is a humus-like substance which is a
valuable soil amendment. Composting organic waste
is a method of converting raw organic materials into a
more decomposed stable product from which plant
nutrients are more readily available.
The main benefit of composting is that it allows the
use of low nitrogen organic materials, such as straw
or woodwaste, without reducing available soil
nitrogen, which would occur if these materials were
added directly to the soil. If adequate time is allowed
for decomposition of crop residues or manures on the
field prior to crop seeding, composting will not likely
provide benefits in addition to those derived from
direct incorporation of underdecomposed organic
materials. Significant amounts of compost can
improve soil structure, water-holding capacity and
supply of plant nutrients.
Compost quality, for non-agricultural compost, is
discussed under the "Production and Use of Compost
Regulation". Not all composts or composting
operations are covered by this Regulation, however, it
does provide guidance for siting, operation and
quality.
Compost made with digested sewage sludge
(biosolids) or large quantities of woodwaste should be
used with caution, since some of these materials may
have high concentrations of toxic metals or harmful
organic compounds. The use of composted biosolids
is controlled by the "Guidelines for Disposal of
Domestic Sludge" and the Waste Management Act
for B.C. Woodwaste should be used with caution as
leachate generated from woodwaste is toxic and can
cause pollution. These may be harmful to some
plants.
For more information on composting, there is a series
of Composting Factsheets available at the Resource
Management Branch, BCMAFF, Abbotsford.
4.5.1.5 Seaweed
Aquatic weeds are useful soil amendments which
provide organic matter and a wide range of plant
nutrients. Seaweed is the most concentrated organic
source of potassium and contains about the same
amount of nitrogen as cow manure. The phosphorus
content of seaweed is quite low.
Seeding of some crops immediately after a heavy
seaweed application may result in reduced emergence
and growth due to high salt concentrations. Seaweed
is inherently saline, so caution should be taken if it is
repeatedly used as a soil amendment. Rinsing with
fresh water will remove residual salt water.
Eurasian Milfoil (freshwater aquatic weed) is
sometimes available in the Okanagan. The organic
74 Soil Management Handbook – Okanagan-Similkameen Valleys