『Abstract
The recycling of organic wastes as soil amendments is notably
promoted in sustainable agricultural systems. However, for many
animal by-products approved by organic farming regulations little
is known about their effects on the greenhouse gas balance of
the soil, in particular on N2O emissions.
In this work we report on the N2O and CO2 emissions from six animal-derived wastes (horn
and hoof meal, blood meal, hydrolysed leather, meat bone meal,
chicken manure and a commercial organic mixed fertiliser). We
compared these emissions to those from a mineral fertiliser (calcium
ammonium nitrate) in a sandy and a loam soil during a three month
laboratory incubation study. N2O flux dynamics
varied strongly with residue category and soil type. In the sandy
soil, cumulative N2O emissions correlated
with soil NO3- content. Although
the mineral fertiliser produced the highest total N2O
emissions (5.7 mg N2O-N kg-1 soil),
the commercial organic fertiliser mixture led to statistically
similar emissions (5.3 mg N2O-N kg-1
soil). The other by-products emitted between 1.3-3.0 mg N2O-N kg-1 soil, and only blood meal
emitted less than 1 mg N2O-N kg-1
soil. In the loam soil N2O emissions never
exceeded 1.0 mg N2O-N kg-1 soil,
and did not correlate with NO3-
in soil. With regard to CO2 emissions and
C storage potential, chicken manure was the only residue that
significantly accumulated C in both soils during the course of
our experiment. The addition of an extra easily available source
of C (glucose) or N (NO3-) influenced
N2O emissions differently depending on the
residue applied. Our results showed that despite the extra amount
of C added with the organic amendments, N2O
emissions from animal-derived wastes were never higher than those
from the mineral fertiliser.
Keywords: Animal meals; Organic farming; Nitrous oxide emissions;
Mineralisation; Soil amendment』
1. Introduction
2. Materials and methods
2.1. Soil and residues used for incubations
2.2. Soil incubations
2.3. Analytical methods
2.3.1. Soils and residues
2.3.2. Measurements of N2O and CO2 emissions
2.3.3. Calculations and statistical analysis
3. Results
3.1. Organic residues used in the incubation
3.2. N2O and CO2 emissions
after residues application (1st incubation experiment)
3.3. Influence of easily available C and N on CO2
and N2O emissions (second experiment)
4. Discussion
4.1. Influence of easily available C and N on CO2
and N2O emissions
5. Conclusions
Acknowledgements
References