Soil and nutrient management: Compost and manure

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Soil and Nutrient Management:
Compost and Manure
Prepared by: Dr. Monica Ozores-Hampton
STEPS TO SUCCESS USING COMPOST:
BENEFITS OF COMPOST AND MANURES:
Compost as a transplant medium: The transplant industry for
the production of tomato and pepper plants relies on peat moss as a
major ingredient in soilless media. Peat is an expensive, non-renewable
resource. Seed emergence and seedling growth was similar to traditional
peat:vermiculite media when peat was partially replaced with compost.
Negative growth effects were reported when the medium was 100%
compost, especially when immature, unstable compost was used
(Figure 1).
Compost as a soil amendment: Amending soils with composted
materials has been reported to increase tomato and pepper yields.
However, combining compost and inorganic fertilizer has generally been
more effective in producing a positive plant response than separate
application of either material alone (Figures 2 & 3).
SOIL AND NUTRIENT MANAGEMENT:
Compost and Manure
Compost may contain
enough micronutrients (trace
elements) to meet the crop’s
annual requirements.
Figure 1. Compost as substitute for potting
soil component. C1 = 18% compost; C2: 35%
compost; C3= 52% compost; C4= 70% com-
post; and C5 = No compost. Photograph by:
Monica Ozores-Hampton.
Figures 2 & 3. (Left)
Reduction in fertilizer use and
higher yields are a few of the
benefits of long-term compost
use. (Right) 0.8% organic
matter in non-composted bed.
Photographs by: Monica
Ozores-Hampton.
After this 10 year study
(to the right), the use
of 3% organic matter
from compost resulted
in 50% less fertilizer.
Soilborne disease suppression: Compost can suppress plant diseases but not all composts and not all the time.
The colonization of compost by beneficial microorganisms during the latter stages of composting appears to be
responsible for inducing disease suppression, especially root-rot diseases and nematodes. Compost does not kill the
pathogens that cause disease as fungicides do. Instead, compost controls the pathogens by keeping the beneficial
microorganisms active and growing. Therefore, pathogenic agents will either not germinate or will remain inactive.
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•Compost must pass applicable federal and state law such as EPA
regulation 40 CFR Part 503 for windrow composting of biosolids:
temperatures of 55oC for 15 days and turned 5 times will eliminate
pathogen and kill weed seeds.
•Meet “horticultural specification” based in crop requirement
(Table 1).
•Compost should be stable and mature, to avoid nitrogen “rob” and
phytotoxic reactions to chemicals (acetic, propionic and butyric acids).
•Compost is not considered a fertilizer; however, significant quantities of nutrients (particularly N, P, K and micronu-
trients) become bio-available with time as compost decomposes in the soil. Amending soil with compost provides
a slow-release source of nutrients, whereas mineral fertilizer is usually water-soluble and is immediately available to
plants.
•Compost usually contains large quantities of plant-available micronutrients. Therefore is important to determine
the nutrient content by a compost certified laboratory. Total N, P and K apply by the compost or manure should
be deducted from the total fertilizer N, P and K annual application rate.

SOIL AND NUTRIENT MANAGEMENT:
Compost and Manure
Prepared by: Dr. Monica Ozores-Hampton
Table 1. Horticultural Specifications for Composted Materials
pH 5.5 – 7.0 In acidic soil, alkaline compost will raise pH
Moisture (%) 35 – 55 Higher moisture, increased handling and
transportation costs
Bulk density (lb per yd3) 800 – 1000 Higher moisture content means a greater
bulk density
Inert and oversize matter (% dry wt) <1
Organic matter content 30-65 % Higher organic matter lowers application rate
Water holding capacity (WHC) (%) 100 or above Higher WHC leads to lower irrigation frequency
Particle size 1’ or less Increase soil porosity
Stability or maturity index Stable to highly stable Instability can cause “N-immobilization”
Maturity growth Must pass maturity screening test GI lower than 60 indicates phytotoxicity
Soluble salts Less than 6 dS Higher than 6.0 means potential toxicity
C:N ratio <20:1 Higher C:N ratio causes “N-immobilization”
Nitrogen 1 % or above
Weed free None Uncomposted materials disseminate weeds
Heavy metals Must pass USEPA, 40 CFR 503
Fecal coliform Must pass USEPA, 40 CFR 503
Salmonella spp. Absent
Other (color and smell) Should have an “earthy” odor that is not unpleasant
z FDACS, 1995
y G.I = (% seed germination x root length growth in % of control) /100 (Zucconi et al., 1981a)
Horticultural Parameter Optimal Range Effect
Biological weed control: Weed growth
suppression is an important attribute of
surface-applied mulch. An organic mulch
suppresses weeds by its physical presence
as a surface cover, or by the action of
phytotoxic compounds that it contains.
Chemical effects of phytotoxic compounds
(volatile fatty acids and/or ammonia) in
compost can decrease weed seed
germination. Inhibition of germination or
subsequent weed growth may be
attributed to both the physical effect of
the mulch and the presence of phytotoxic
compounds (fatty acids) in the immature
compost (Figure 4).
Figure 4. Application of 3 inches
or more immature compost in the
row middle in vegetable beds
suppressed weeds significantly.
Photograph by: Monica Ozores-
Hampton.
Figure 5. Application of Municipal
Solid Waste compost as a
polyethylene mulch replacement in
a pepper field. Photograph by:
Monica Ozores-Hampton.
Polyethylene mulch alternative: Removal and disposal of polyethylene mulch has been a major production cost
to Florida growers. Polyethylene mulch regulates soil temperature and moisture, reduces weed seed germination and
leaching of inorganic fertilizer, and is a barrier for soil fumigants. In general traditional raised beds were covered with
polyethylene mulch or replaced by composted materials bell pepper yields were higher on compost mulch plots than
on un-mulched plots but lower than on polyethylene-mulched beds (Figure 5).
More Benefits of compost:
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How to calculate compost application rates for
tomatoes based on crop N requirements:
10 tons of compost x 60% dry weight = 6 tons compost
dry weight
6 tons dry weight x 3 % N = 360 lb of N
360 lb of N x 10% mineralization rate
36 lb NO3-N if the tomato requirements are 200 lb/acre
we need to added 164 lb of N as a N fertilizer
Prepared by: Dr. Monica Ozores-Hampton
It is important to know the mineralization (decomposition,
or microbial break-down) rate of the compost before
determining its application rate to tomatoes and peppers.
The rate of nitrogen (N) release is especially important,
since this nutrient moves readily through sandy soil.
Evaluations of N mineralization in situ can be used to improve
N use efficiency. However, the direct, quantitative
measurement of N mineralization in situ is very difficult due
to the complex and dynamic nature of N transformations in
the soil environment.
Compost mineralization rates will vary depending on compost
characteristics, soil characteristics and environmental
conditions. As general recommendations where N
immobilization occurred, composts had initial C:N greater
than 20:1 and N concentration less than 1.6%. Mineralization
occurred where compost had C:N ratio lower than 20:1
and N concentration greater than 1.6%.
SOIL AND NUTRIENT MANAGEMENT:
Compost and Manure
HOW AND WHEN TO INCORPORATE?
NUTRIENT RELEASE:
Figure 7. Localized application of compost directly to
bed. Photograph by: Monica Ozores-Hampton.
Figure 6. Broadcast application using a manure
spreader. Photograph by: Monica Ozores-Hampton.
HOW TO CALIBRATE A COMPOST
SPREADER:
•First load and weigh the contents of the spreader
or weigh a 5-gallon bucket of manure and multiply
the weight x 1.5 x length x width x height of the
spreader. This will give you tons per load of compost
or manure.
•Next determine the distance in feet that it takes to
spread the entire load. Distance can be estimated
or determined based on known field length or by
counting fence posts along the length of the spread
and multiplying by the average distance between
posts.
•Then estimate the width of the spread in feet,
allowing for a 10-20% pass overlap to ensure uniform
coverage. Calculate the area covered and divide by
43,560 to convert to acres. Divide the weight or
volume of manure in the spreader by the acres
covered to determine the application rate for the
given spreader setting (length x width of spread /
acres covered = application rate in tons or gallons).
Adjust the spreader settings and redo the
calculations until the desired application rate is
achieved.
•Compost may be applied using a traditional manure
spreader (flail/rear discharge or side discharge) or other
specialized equipment.
•Compost is typically applied throughout an entire field,
but may also be applied only in the rows. The product
should be uniformly surface-applied, then incorporated
to an approximate depth of 5 to 6 inches using a rototiller,
disc, moldboard plow or other tillage equipment.
•Tomatoes have been cultivated using a wide range of
compost application rates of 5 to 70 tons/acre. Lower
rates of compost are typically being used as “maintenance
applications.” Appropriate compost application rates will
be influenced by existing soil conditions, compost
characteristics and the nutrient requirements of the crop.
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SOIL AND NUTRIENT MANAGEMENT:
Compost and Manure
CONTACT INFORMATION:
Dr. Monica Ozores-Hampton
UF/IFAS SWREC
2686 State Rd. 29 North
Immokalee, Fl 34142-9515
239-658-3400
ozores@ifas.ufl.edu
Website: www.Imok.ufl.edu/Compost
• Use of immature compost can cause detrimental effects on tomato and pepper growth (Figure 8). Compost should
be assayed for the presence of phytotoxic compounds using phytotoxicity test and seedling growth responses.
• Tomato and pepper crops are sensitive to high soluble salts, especially when they are direct-seeded. Measuring the
soluble salts concentration of a saturation extract recommended. If the electrical conductivity (EC) is below 6.0 dS/
m, no salt toxicity is expected. If EC is above 6.0 dS/m, the amended soil should be leached with water before
planting seeds (only a few crops can tolerate this salt level).
• High C:N compost can result in N immobilization or
“rob”. Have the compost analyzed for C:N ratio. If it
is above 20:1, some N fertilizer applied to the crop
may be immobilized due to N immobilization, possibly
causing plant N deficiency. When using compost with
C:N ratios higher than 20:1, N fertilizer should be
applied, or planting delayed for 6 to 10 weeks to
allow the compost to stabilize in the soil.
• Lack of equipment to spread compost in vegetable
fields is a concern. Composting facilities are
encouraged to play an active role in developing
spreading equipment.
AVOIDING PROBLEMS:
Compost can be produced from a variety of feedstocks,
including organic amendments from wastes produced
by urban populations include municipal solid waste;
yard trash/trimmings; food wastes from restaurants,
grocery stores, and institutions; wood wastes from
construction and/or demolition; wastewater (from
water treatment plants); and biosolids (sewage
sludge).
Agriculture produces other organic wastes that can
be composted: poultry, dairy, horse, feedlot and swine
manures; wastes from food processing plants; spoiled
feeds, harvest wastes and mushroom media.
SOURCES OF COMPOST AND MANURE:
Figure 9. Interested in compost? Attend a compost
field-day or training event to learn more about how
compost can improve your production system.
Photograph by: Monica Ozores-Hampton.
Visit www.Imok.ufl.edu/Compost for more information,
research results and more.
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Figure 8. Foreground: Pepper growth is stunted by
phytotoxic chemicals in immature compost. In the
background peppers with mature compost are
thriving. Photograph by: Monica Ozores-Hampton.