Potential Environmental Impacts of Uncomposted Organic Materials, Composts and Manures
Raina SK*, Chohan A, Singh P and Ram D
Directorate of Extension, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, India
Submission: May 05, 2018; Published: July 10, 2018
*Corresponding author: S.K. Raina, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Shalimar, Srinagar, J&K, India–190 025, Email: [email protected]
How to cite this article: Raina SK, Chohan A, Singh P, Ram D. Potential Environmental Impacts of Uncomposted Organic Materials, Composts and
Manures. Eng Technol Open Acc. 2018; 2(2): 555581. 10.19080/ETOAJ.2018.02.555581
Soil health is central to organic farming and organic inputs are applied to improve it so as to get higher economic yields on sustainable basis. A lot of work has been done around the world to support this fact. But there are environmental concerns related to the use of inputs which include the losses of nutrients from the farming systems to the open ecosystems causing damage to the water bodies including underground water contamination. Gaseous nitrogen losses tend to be lower from composted than fresh organic materials. There is a need to investigate trade-offs between different gaseous and leaching forms of pollutants following compost application. The environmental impacts of organic materials including uncomposted and composted manures applied to the soil to get higher production and productive of crops, have not been studied by many. This review paper is an attempt to summarize the same.
Soil health is central to organic farming, but its potential has not been fully explored. Soil is a living dynamic system that functions in a holistic way depending upon its condition or state. Its reflection can be seen in terms of our own health. And phrases such as soil sickness, feeding the soil etc take on a real meaning when soil is managed and treated as a vital living system.
Soil health has been formally defined as “the capacity of a specific kind of soil to function as a vital living system, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation.”
Organic farming systems are dependent upon the management of soil organic matter which enhances the chemical, biological, and physical properties of the soil, in order to optimise crop production. This subject has been reviewed by Watson et al. . Soil management has a bearing on the supply of nutrients to crops, and inturn to livestock and humans. In addition to symbiotic N fixation and atmosphericdeposition, nutrients may be brought in to the organic system in the form of off-farm animal feeds, manures, composts and permitted fertilisers, such as rock phosphate . Soil type and its inherent nutrient supplying capacity will decide the type and quality of fertilizers to be supplied. Watson et al.  highlighted that
horticultural systems are dependent upon purchased manures and other organic inputs.
Though there is a vast literature available which indicates the positive effects of the organic materials including compost and manures on soil health; there is meagre work reported showing the environmental impacts of use of undecomposed organic materials, decomposed organic manures and compost. Here, it has been tried to review the literature regarding potential environmental impacts from the use of organic materials.
Generally, nitrate nitrogen leaching begins immediately after its level in soil exceeds the demand by the crops when enough drainage volume is present. In organic farming systems nitrate accumulates from both added organic matter and mineralization of soil organic matter. Initial N content of the organic material does not always indicate the potential for leaching as the nitrogen content in mineral and organic forms varies tremendously. As reported by Di & Cameron  the mineral nitrogen contents (% total N) ranged from 15% in anaerobic dairy sludge to 60-85% in pig slurry.
Leaching loss depends a lot on the time of application of manures. Application of dairy waste in four splits resulted in lesser leaching of nitrogen when same amount was applied in two
splits, because there was more synchronisation between supply
nitrogen and demand of nitrogen by the pasture . Method
of application is also important as far as the environmental
contamination from the use of organic inputs is concerned.
Application of fresh and composted biosolids increased the risk
of P and metal leaching, But, had no effect on nitrate leaching as
observed by Gove et al. .
Not much work has been reported, comparing leaching
loss from composted and fresh material. lysimeter experiment
conducted by Leclerc et al. , in which the concept of leaching/
supply ratio was used to study the effects of different organic
amendments across a rotation, revealed that the ratio was lower
for composted manure than for urban compost. Vervoort et al.
 reported lesser nitrate leaching from composted than fresh
chicken manure. There may be the possibility that the capacity
to immobilize nitrogen from high C:N ratio wastes is responsible
for its lower leaching. For example, Vinten et al.  demonstrated
a drop in leaching from 177 to 94kg N ha-1yr-1 in vegetable
production system when 40tha-1 dry matter of paper mill waste
Use of municipal solid waste compost can reduce degradation
of surface structure, thus decreasing losses by runoff and erosion
. Composted as well as non-composted municipal wastes have
the ability to reduce runoff and erosion as proved by Ros et al.
. Though, both treatments reduced runoff in amended soils
as compared with unamended soil, but compost has an edge in
reducing soil loss over less stable material.
Loss of phosphorus in runoff from applied manures is
determined by the type of manure and crop. Sharpley and
Rekolainen  quoted losses of from 1.9 and 17.1% of applied
P in manure lost in run-off. The main hurdle in minimising this
loss is the inability of the farmer to apply at right time which
is due to the lack of adequate storage facilities with the farmer.
No difference in the levels of soluble phosphorus in runoff from
composted and fresh chicken manure was observed by Vervoort
et al. , inferring that runoff is directly correlated with the
amount of phosphorus applied to soil. Sharpley and Moyer
 recorded the release of dissolved organic and inorganic
phosphorus from simulated rainfall events from a range of
slurries and manures applied at the equivalent of 10Mgha-1.
About 10% of ammonia emissions in Europe is due to
the emission of ammonia from field applied manures .
A complex relationship exists between ammonia emission
rates from slurry and soil conditions, slurry composition and
climate Sommer and Hutchings . Meagre research work
is available on solid or poultry manure. Aerobically stored
manures when applied to field cause more ammonia losses as
compared to anaerobically stored ones . Ammonia loss from
slurry is directly proportional to the dry matter content .
A comparison was made between ammonia volatilization from
surface applied fresh and composted poultry manure under
laboratory conditions. Total ammonia loss for a 21day period
varied from 17-31% from fresh material compared with 0-0.24%
from composted material. Method of application such as slurry
application to ploughed land and manures incorporation into
cultiviable land have been proved to decrease ammonia loss over
surface application .
Annual nitrous oxide emissions are directly proportional
to manure application rate . Kaiser et al.  reported an
inverse relationship between nitrous oxide emission and dry
matter to N ratio of incorporated crop residues. However, few
studies have compared annual nitrous oxide losses from field
application of different organic materials. Mogge et al. 
compared losses from slurry and FYM application to maize. About
5.7% of applied nitrogen (equivalent to 5.3kgha-1) was lost as
nitrous oxide in the FYM treatment as compared to compared
only 0.6% of applied nitrogen in the slurry treatment (equivalent
to 2.1kgha-1). No significant effect was recorded with the
addition of 30Mgha-1 household compost on cumulative nitrous
oxide production as compared with an unamended soil, in a
laboratory incubation experiment done by De Wever et al. .
Further it was concluded that the use of compost as a fertilizer at
normal agronomic rates would not have much effect on nitrous
oxide production. Contrasting results have been observed for
sewage sludge in field trials. A cumulative loss of 23kg nitrogen
ha-1 along with high carbon dioxide losses of 5.1MgCha-1 from
incorporated sewage sludge was recorded by Scott et al. .
Some scientists like Stephenson  have suggested that
the use of manures and organic food without preservatives
may mean a high level of microbial contamination of organic
food. The organic standards, however, prevent the use of fresh
manure and require good management practices in the storage
and handling of manures and composts. Both composting of
farmyard manure [23,24] and anaerobic digestion of slurry 
have been reported to decrease pathogen viability. There have
been a number of claims of E. coli (O157:H7) outbreaks being
associated with organic food  but none of these claims have
ever been proven. There is no concrete evidence in the form
of research reviews which prove that certified organic food
contains any traces of E. Coli as compared to the conventionally
produced food. Advanced research should be carried out to
standardize the microbiological risks associated with different
Mawdsley et al.  reported that 11 bacteria, 3 viruses
and 4 protozoa/parasites were present in livestock waste which
may cause human disease. Contamination of ground and surface
waters with pathogenic organisms can be caused by application
of animal wastes on land . These contaminats from ground
water can be transmitted to both humans and livestock. E. coli, and especially verocytotoxin producing E. coli, including
serogroup O157 is excreted by as much as 15.7% cattle in the
Very high concentration E. coli in field drains were recorded
after application of slurry, but low-level contamination persisted
for 3 months only [30,31] quotes a review by Sorber & Moore
 summarising data on survival of microorganisms from
biosolids applied to soil. The median die-off rate (days, 99%)
was 155 for total coliforms in the top 5 cm of soil, and 22 and 30
days for Salmonella in the 0-5cm and 5-15cm soil layers.
Urban wastes are fully of heavy metal contaminants. This
problem is also with animal manures where metals are present
in their feed e.g. Cu in pig and poultry feeds. Many fungicides
contain Cu, Zn or Mg and their residues may remain on
composted organic matter . The level of potential toxicity
increases exponentially in a hierarchical manner in a food
chain which must be considered in perspective of human and
animal health. The pattern of release of plant available metals
from decomposition of organic materials cannot be predicted
from laboratory extractions. For example, Arnesen & Singh 
observed that application of compost increased plant Cu levels
but not DTPA extractable Cu but the reverse was true for Zn.
Type of soil will determine the pattern of release of available
heavy metals and nutrients elements, which depends upon the
leaching/adsorption properties of the soil which in turn depends
on pH, texture and organic matter content of soil. Plots treated
with organic manures showed less available copper than control
plots in spite of having high levels of copper in manures, thus
demonstrating moderating effect of soil .
From a review of 96 articles on phytotoxicity caused by metals
from municipal solid wastes, from a review it was concluded that
plant uptake of Cu, Ni, Zn, As and Pb was less although municipal
solid wastes were used as source of nutrients . It was further
inferred that boron levels would have no deleterious effect
inspite of its increasing levels in soil. Modern manufacturing
processes have changed the compositions of waste materials
and thus, the old literature may not give the correct picture
about the toxicity effects of waste materials. Regulation also
limits the application rate of potentially toxic elements from
sewage and sludge. Giusquiani et al.  observed that total
heavy metals accumulation in soil is directly proportional to
the rate of application of urban waste compost. Application of
mixed compost of paper sludge and chicken manure increased
the available Mn and Zn content in soil Baziramakenga et al. .
In acid soils, additions of organic residues decreased
exchangeable Al in the order poultry manure>filter
cake>household compost>grass residues when same number
of residues were applied Mokolabate & Haynes . It was
suggested that this may be due to the high CaCO3 content in the
case of poultry manure and filter cake, the proton consumption
capacity of humic material present in the household waste and
decarboxylation of organic acid anions during decomposition of
the grass residues.
Gaseous nitrogen losses tend to be lower from composted
than fresh organic materials, but management options to
minimise these losses need further development. There is a need
to investigate trade-offs between different gaseous and leaching
forms of pollutants following compost application. This should
include methane and carbon dioxide. There is little information
on pathogen persistence and movement in soils/water following
spreading. Gaseous and leaching losses from the use of compost
need to be assessed in the context of the farming system rather
than for individual crops.