Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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In land utilization the consumption of inorganic plant nutrients, so-
called commercial fertilizers, has greatly :increased in recent years. Such
fertilizers contain nitrogen, phosphorous, potassium and trace substances
essential to the plants. Normally, these chemical elements are present in
chemical compounds which are readily dissolved in water and which can therefore
be rapidiy leached out from the top soil layer by rain water and carried
therewith into water-ways and lakes, creating serious environmental problems.
Consequently, when plant nutrients are administered in the form of commercial
fertilizers great losses are often experienced.
When commercial fertilizers are used annually over long periods
of time, contaminants in the form of heavy metals are liable to collect in
the ground, in a chemical form such as to be drawn into and be concentrated
in the plants. Heavy metals can also be found in excessively high concentrat-
ions when untreated digested sewage sludge from sewage works is used as a
fertilizer.
The present invention is based on the discovery that it is possible
to create a durable physical and chemical environment which enables a plant
nutrient to be supplied to the roots of the plants with much greater
efficiency yield) than was previously considered possible. By practicing
the present invention it is possible to significantly improve the harvest
yield i.e. to produce larger harvests per ground area and amount of nutrient
supplied.
According to one aspect of the present invention there is provided
a method for increasing harvest yield in plant cultivation, comprising
supplying to the soil plant nutrient depots comprising a mixture of bark and
peat, which mixture has been composted and compressed in an extruder press to
form pellets having a water content of about 10 - 15% by weight.
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According to another aspect of the present invention there is
provided a plant nutrient product comprising an extruded pelleti~ed mixture
of bark and peat wherein the pellets are about 5 - lO mm in diameter and
about lO - 15 mm in length.
The mixture advantageously includes plant nutrient substances,
preferably including a source of nitrogen, phosphorous or potassium which may
be added prior to or after composting.
In a preferred embodiment of the above method the peat and bark
mixture includes a component which has one or more of the rollowing properties:
lo high bacteriological activity,
2) plant nutrition in a form available to the roots,
3) water retaining ability,
4) binding capacity at pressing,
5) capacity for chemical binding of heavy metals, wherein the component
is mixed with the peat and bark and then the mixture is pressed together under
high pressure.
Fermented peat provides properties l), 3) and 4); conventional water-
soluble plant nutrients containing nitrogen, potassium, phosphorous and trace
elements can be used to provide property 2); composted bark provides properties
l) and 5); composted biological sewage sludge from a water purification plant
provides properties l), 2) and 3); and composted organic waste material e.g.
from households, provides properties l) and 2).
Advantages of the invention reside in providing the soil not only with
nutrients as such, but also simultaneously with a chemical, physical or
biological environment required in order for the plants, through their roots,
to utilize the nutrients, while any surplus of nutrients remains in the soil
from one growing season to the next.
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In accordance with the invention, the nutrient substances are
incorporated and adsorbed in pellets of a compostible and composted, ground
biomaterial, such as finely-divided bark of conifers, de-watered and shredded
peat, disintegrated newsprint, compostible and composted fractions of
domestic waste, straw and common reed, either with OI` without the addition
of fresh or digested sludge from communal sewage works. The surprisingly
high yield which can be obtained when praticing the invention is illustrated
in the accompanying drawingsin which:
Figure 1 is a graph showing the effect of increasing amounts of
springspread (SS) nitrogen with pellets, P 1, and commercial fertilizer
nitrogen (KAS, 28% N) on grain harvest; and
Figure 2 is a graph showing the effect of increasing amounts of
autumnspread (AS) nitrogen with pellets, P 1, and springspread (SS) commercial
fertilizer (KAS, 28% N) on grain harvest.
Figure 1 illustrates the harvest yield when administering various
nitrogen additions, on one hand as commercial fertilizer, KAS, and on the other
hand as plant nutrient pellets, Pl, according to the present invention. It
will be seen from Figure 2 that even when the nutrient substance according to
the invention is administered in the Autumn, about six months before the seed
is to be sown, the yield per hectare and amount of nitrogen supplied is
greater than when nitrogen is administered in the Spring under otherwise
similar conditions.
This shows that the present pellets create a depot effect in the soil
with regard to distribution of plant nutrients, the addition of microbiological
activities, and other factors, which are essential for a good harvest. At the
same time as the nutrient effect greatly increases in accordance with the
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illustrated diagram, any heavy metals present are bowld to the bark in the form
of insoluble so-called chelate compounds, which prevent the plants from taking
up heavy metals, or reduces the extent to which such metals are taken up.
EXAMPLE
Bark having a dry weight content of 250 kg was shredded to a particle
size of at most 5 Inm and was mixed thoroughly with de-watered peat having a
dry weight content of 250 kg and containing other disintegrated biomass. The
mixing continued until a homogeneous mass having an optimal water content with
regard to composting was obtained. This mass was composted in a vertical
reactor vessel, while continuously aerating the mass and turning it over.
During the composting process the mass is heated to 70C for long enough that
any pathogenic bacteria present are destroyed.
Composting involves a biological degradation of the biological mass
involved, which leads to a stabilization of the organic material, and the
mixture is sterilized by the heat generated, as mentioned above. This is
particularly important when digested sludge from sewage is included. Intended
plant nutrients were added to the composted mass in a chemical form to prevent
the nutrients prom escaping during the manufacturing process. The plant
nutrients can also be added prior to the composting process.
The enriched mixture having a moisture content of about 45% was
compressed to a relatively high density about 0.8 - 1.0) and was formed into
pellets in a pellet extruder or pelletizing machine, the pellets being dried
and cooled, whereby mechanically very strong pellets were obtained. Pelletizing
also facilitates handling, transportation, and spreading of the product.
The ready-to-use pelleted product had a moisture content of 10 - 15%
by weight, which is a reasonable level to prevent microbiological activities
occurring during storage.
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When compressing the miY.ture during the pelletizing process the
nutrients are adsorbed on, and bound with, the organic material, and are
slowly released in the soil in keeping with the take-up ability of the plants.
Such trace elements as Mg, Mn, B, Co, and Cu can also be added to the
homogeneous mass together with the plant nutrients prior to the pelletizing
process.
The composted organic content of the pellets increases the biological
activity when mixed with the soil, and provides for an extended fertilizing
effect aftereffect The biological material present, bark, and peatJ
shows moreover an ability to bind water, whereby the water-retention provides
for a suitable environment for the nutrient uptake.
In a preferred embodiment cf the invention bark, peat, and sewage
sludge are mixed in a dry weight ratio of 25:25:50 and are provided with plant
nutrients in a suitable form. The mixture is then pelletized, and introduced
into a reactor to be composted by means of a continuous aeration. After
composting,the pellets are applied to the soil in a conventional manner.
While pelletizing, seeds can be added to the mass which is to be
pelletized, whereby a product is obtained which provides good initial conditions
for germination and nutrient dissipation during the initial period in the soil.
By using a water retention ability, the biomass acquires good conditions for
the seed, and the risk of seed destruction by dehydration is reduced.
