THE CASE FOR PURCHASING TERRAMAX ORGANIC
FERTILISER, INSTEAD OF STOCKPILED FEEDLOT MANURE
TerraMax Pty. Ltd. have developed a Quality Assured process for composting feedlot
manure, to produce a hygienic, uniform product that can be applied to both food and fibre
crops. Accredited under the SCI QUAL, HACCP-based certification, the management of
elevated temperatures within the core of the windrows and regular turning (Critical
Control Points) destroys hazardous biological agents such as animal and plant pathogens
and weed seeds. The combination of microbial activity and turning produces an even
crumb structure, increasing the water and nutrient-holding capacity of the compost. As
part of the HACCP process, Enviroganics dries the product to 33% by weight of water,
prior to screening before sale.
Variability in the Composition of Feedlot Manure
The composition of manure varies substantially due to differences in storage and handling.
Depending on the construction of the feedlot pad, the soil type, method and timing of manure
removal, the water content and the degree of soil contamination will also vary substantially.
Contaminants include animal and plant pathogens, weed seeds, and stones. The more water, soil
and rocks, the higher the costs of transport, the more variable the application rate over a field,
and the greater the risk of damage to tillage and harvesting equipment. These differences also
have a huge impact on the concentration of key plant nutrients such as phosphorus (P), potassium
(K) and nitrogen (N), with water and soil diluting their value. Moreover, on a manure collection
pad, there is no effective control over the survival of plant and animal pathogens, and weed
seeds. Thermophilic (high temperature) composting (Figure 1) overcomes much of this
variation, producing a more uniform, hygienic, friable, and biologically stable product.
Figure 1: Turning windrows is necessary to ensure that all components of the compost have
been exposed to the elevated temperatures within the central core. The
combination of moist heat, and the change in the activity and diversity of the
microbial population over time (Critical Control Points) kill most weed seeds and
pathogens, and minimise the risk of pathogen re-contamination.
1
18
16
load 1
load 2
kg per ton field weight
14
12
10
8
6
4
2
0
nitrate
ammonium
available P
total K
calcium
Figure 2: Variation in the concentration of plant-available nutrients present in two
consecutively transported loads of cattle manure collected from the one feedlot.
Data courtesy of a Macalister farmer 1999.
The Effect of Composting on the Particle Size and Nutrient Concentration of
Manures and Other Organic Materials
Stockpiles of manures and other organic waste (eg cotton trash) have been incorrectly referred to
as compost. Strictly, a compost is organic material which has been subjected to moist heat for a
sufficient period of time to exhaust all of the readily available organic carbon (refer Can Do
Sheet 4 on Co-Composting). The heat-loving microbes require high levels of moisture, air and
readily available organic materials for activity. The heat generated by microbial activity is
trapped within the matrix of the windrow (thermal mass), killing weed seeds and pathogens.
The concentration of plant-available nutrients increases and stabilizes, and humus-like
compounds are produced as readily available organic matter is exhausted (biological maturity).
The mechanical turning and microbial activity breaks down clods of manure, producing a finer
textured material. At this stage of processing, no water is added, enabling the compost to dry to
about 30% by weight water for ease of storage, handling and transportation. Under the Sci Qual
(HACCP) Quality Assurance accreditation, TerraMax screens all dried, mature compost
through a 10 mm aperture mesh to remove contaminants such as stones, cement, steel and
plastics.
Microbes will also be active in manure stockpiles. However, the process is uncontrolled, with no
reliable tests available for measuring the degree of biological maturity achieved. The degree of
biological maturity is important, because it affects the availability of nutrients for plant uptake.
Microbes may grab all of the available nutrients, in quantities above that required for cell
maintenance and growth (compare the difference in available P in Figure 2, and refer to Figure
3). This process also occurs after manure is added to soil, resulting in nutrient draw-down
(mainly N and P, as in Figure 3). Depending on the rate of application, the enhanced microbial
activity can starve plants, and deplete the soil of oxygen. At temperatures between 50 and 700 C
within a managed windrow (optimal for composting), microbial decomposition is much faster,
2
and changes in biological stability can be monitored.
3
0.9
0.8
avail:total N
1.63
1.33
avail:total P
1.62
avail:total K
0.7
0.6
0.5
0.4
0.31
0.13
0.3
0.2
0.1
2.50
1.71
0.24
2.42
0
week 1
week 14
week 22
Figure 3: Changes in the plant-available and total nutrient concentration of a cotton trash
compost over time. The ratio of plant-available to total N and P reduces
substantially as microbial activity increases (compare the height of the first and
second bars for weeks 1 and 14). By the end of composting (week 22) the
availability of N and P has returned to pre-composting levels. The difference is
that after adding the mature compost to soil, this value will not change (no
nutrient drawdown). The total concentration (numerals above the bars) has
increased for N and P (1.71 and 0.13% by dry weight in week 1 to 2.42 and 0.31%
by week 22). K remains mostly water-soluble over the entire composting process,
and can be lost if excessively watered (1.63% in week 1, 1.33% by week 22).
Using Animal Manures and Composts as Fertiliser Substitutes.
In the past, application rates for animal manures and composts have been calculated according to
their total N concentration. This is extremely misleading, for three reasons :1. The vast majority of N in animal manures and composts is in the organic form (NOT
plant-available, refer to Figure 3)
2. The nutrient most readily available is potassium (K), which is responsible for the
immediate plant growth responses observed after application, but excessive applications
can burn plants (refer to Can Do Sheet 14 on Composts as Mulches)
3. Applications based on N may overload the soil with P, leading to nutrient pollution of
waterways (algal blooms) and nutrient imbalance in crops (plant disease, lodging).
To maintain soil health and to reduce the costs of production, the nutrients applied in animal
manures and composts must be subtracted from the conventional fertiliser application rates
recommended for that crop or pasture. With uncomposted organic byproducts, this is difficult,
because the plant-availability of N and P will vary at the point of purchase, during storage, and
after application to soil (refer to Figure 3 and Table 1). The rate of application with
uncomposted manures is also highly variable, due to the cloddy nature of the raw material.
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Value
Stockpiled
feedlot
manure
Composted
feedlot
manure
Highest
Lowest
Average
Highest
Lowest
Average
Total N
kg per ton
30.0
10.0
21.8
32.0
24.0
28.4
Total P
kg per ton
13.0
4.0
8.0
18.0
10.1
13.6
Total K
kg per ton
40.0
15.0
23.2
26.7
19.3
23.6
Total Ca
kg per ton
21.0
7.3
16.0
71.8
33.2
49.5
Water
kg per ton
500
100
300
447
333
383
Table 1: Chemical analysis of the Total (plant-available plus slow-release organic) nutrient
concentration in feedlot manure as collected from different feedlots (data
courtesy E Powell), and co-composted by TerraMax with sawdust and grain dust
to biological maturity. The TerraMax compost was sampled from windrows prior
to final drying and screening.
TerraMax composts also contain more organic carbon than feedlot manure (average of 24% on
a dry weight basis), as sawdust is added to improve microbial processing. The humus-like
compounds produced towards the end of the composting process have many soil health
advantages (refer to Can Do Sheet 5 on Doing Your Own Field Trials), including increasing
the nutrient (cation exchange capacity) and water-holding properties of the soil. The TerraMax
compost has a cation exchange capacity of 120 meq per 100gm, over ten times that of some
sandy cropping soils, and close to twice that of self-mulching black vertisols.
Application rates should be based on the available K requirements of the crop, as shown in the
table below. Once the upper application rate has been established, multiply the available P value
(expressed as kg per tonne) by the dry weight equivalent of the application rate (kg per ha, refer
asterisks** in table), and subtract these values from your conventional fertiliser requirements.
The rate of release of the organic N and P in the compost will depend on the moisture available
in the soil and the temperature. Currently, only soil tests will indicate when these nutrients
become available to your crop.
PROCEDURE
COMMENTS
YOUR CALCULATIONS
Compare potassium (K)
required to meet next crop’s
requirements with the plantavailable concentration of K in
the compost (dry weight basis).
Multiply the mg/kg bicarbonate
or Olsen- extractable K
concentration by 1,000 to
convert to kg per ton.
Use this value to calculate the
tons per ha of compost needed
Crop K required
Adjust the application rate of
compost required to meet the K
needs of the crop for the water
content of the compost (water
dilutes the nutrient value of the
compost so more compost must
be applied to meet the crop’s
requirements)
If the compost is 30% water,
then the actual K concentration
(‘active ingredient’) is only
70% of the asterisked value
above (**). This value will need
to be multiplied by 100 and
divided by 70 (reciprocal of the
‘active ingredient’ value) to
make up for this dilution factor
5
Available K in compost (tons
per ha dry-weight basis)
Tons per ha of compost to be
applied (dry weight basis)**
Water concentration in compost
Concentration of ‘active
ingredient’
Actual tons per ha of compost
to be applied ## (field weight
basis)
CALCULATING THE COST EFFECTIVENESS OF TERRAMAX COMPOST.
TerraMax compost is sold at 30% moisture. As shown in Table 1, the concentration of water in
stockpiled feedlot manure can be as high as 50%. Water and stones dilute the nutrient value of
manure, and feedlots rarely provide chemical analyses of the total and plant-available nutrient
composition of different stockpiles. The batch composting and HACCP-based Quality Assurance
testing undertaken by TerraMax ensures that the risks of spreading pathogens or weed seeds, or
buying in stones, is minimal. The variation in the concentration of nutrients in different batches
of TerraMax compost is also much less than that in stockpiled feedlot manure (Table 1), as the
process is controlled and monitored, and all compost is processed to biological maturity. A
comparison of the fertiliser value of TerraMax compost is provided in Table 2.
Fertiliser
standard
Price per tonne
(including GST)
%element per ton %element per ton Equivalent %
value per tonne
TerraMax
TerraMax
Urea N
Phos starterZ
Potash K
Gypsum Ca
Sulphur startZ
Trace elements
$655.00
$905.00
$650.00
$ 165.00
46% N
21.9% P
50% K
18.5% Ca
14%
2.5% N
1.0% P
2% K
4.5% Ca
0.7% S
Cu, Zn, Fe, Mn
$35.00
$41.00
$26.00
$40.00
$ 8.00
$35.00
Total $ value
$185.00
Table 2: Comparing the fertiliser value of TerraMax compost and conventional fertilisers.
The % concentration listed for TerraMax compost is Total nutrients. For N, P and
K assume 10%, 30% and 80% respectively is in the plant-available form at
application. The rest is organic (slow0-release), becoming available as soil water
and temperature conditions stimulate microbial activity (mineralisation). The
slow-release nutrient bank resists deep drainage, and release is activated by the
same seasonal conditions that stimulate plant growth.
In addition to plant-available and slow-release nutrients, TerraMax has 22% by weight of
organic carbon. In practice, at an application rate of 5 tonnes per ha (3.5 tonnes dry weight) an
additional 770 kg of stable organic carbon has been added to the soil. This is more than the
additional organic carbon added to soil if a pasture phase of 1 year is used instead of planting a
crop. The increased microbial diversity, the increased water holding and cation exchange
capacity associated with this application has many advantages for soil health. However, putting a
dollar value on improved water infiltration, nutrient availability and microbial diversity is only
possible over time, based on personal experience.
More information on the topic of composting and soil health is available in the ‘Can Do’
series of information sheets, available on www.grubbclc.com.au
Dr Pam Pittaway (Soil Scientist and Microbe Biologist) of Chrysalis Landscape
Consultants assisted in the preparation of this brochure, and also publishes the ‘Can Do’
series. She can be contacted at grubbclc@bigpond.com
Sheet updated 5/8/2004
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