In this book some of the research carried out
by part of the members of the Spanish Group of Soil Enzymology are
summarized.
The chapters are both in English and Spanish. Those studies are a
reflection
of the increasing interest that Soil Enzymology has awaken in the
Spanish
science community in the last years. A wide range of topics are dealt
with
in this book: use of enzymes as indexes of soil quality, influence of
microbial
activity in degradation and desertification processes in soils, enzymes
and
soil fertility...
Contents
- Preface. Paolo Nannipieri
- Indexes of biological activity as
tools for diagnosing soil fertility in organic farming. R. Canet,
R. Albiach and F. Pomares
A
deep understanding of how enzymatic systems work is extremely important
in
organic farming, since fertilization in this sort of practice depends
almost
entirely on the biological fixation of nutrients and the decomposition
of
organic matter. In spite of this, very few articles have been published
on
the enzymatic activity of organically managed soils. In this chapter,
we
bring together and summarize the main studies on the subject carried
out
in Spain and analyse expected future trends.
- Microbial activity in soils of SE
Spain exposed
to degradation and desertification processes. Strategies for their
rehabilitation. C. García, M.T. Hernández, J.A.
Pascual,
J.L. Moreno and M. Ros
Soil
microbial activity measurements are an useful tool in the study of soil
quality
since microbial activity is a good index of microbiological and
biochemical
soil fertility. Soils of Mediterranean SE Spain, which are submitted to
semiarid
climatic conditions, show a high degradation degree as a consequence of
the
employ of inappropriate agricultural practices, which lead to the lose
of
soil fertility and to the consequent soil abandonment. Soil degradation
and
abandonment for agricultural use in this Mediterranean area is
frequently
motivated by the use in irrigation of saline waters which causes a
progressive
salinization of the soil. This lose of microbial activity and soil
quality
can be detected through various bioindicators such as microbial biomass
carbon,
soil respiration and some enzymatic activities. Different field
experiments
aimed to reach the rehabilitation of degrades soils have been carried
out.
For this purpose the strategy followed has been the addition to
degraded
soils of the organic fraction proceeding from urban wastes as soil
organic
amendments. This practice has revealed as a good technique to improve
the
quality of degraded soils.
- Biochemical properties of the soil
of Galicia (NW Spain): their use as indicators of soil quality. C.
Trasar, M.C. Leirós, F. García and F. Gil
This
chapter summarises the results of work carried out by the authors'
research
group on the biochemical properties of the soils of Galicia (NW Spain),
with
special emphasis paid to hydrolytic enzyme activities. The biochemical
properties
of the förna layers and upper Ah horizons of native soils under
climax vegetation
(Atlantic oakwood) show wide seasonal and geographical variations, and
also
exhibit well-characterised relationships with their physical and
chemical
properties. The annual mean values of the biochemical parameters are
approximately
equal to their mean value during the autumn. In a study of long-term
sample
storage methods, the methods causing least distortion of biochemical
parameters
were refrigeration at 4ºC and freezing a -20ºC. The
equilibrium between the
organic matter content and biochemical properties in the climax soils
is
reflected by close correlation between Kjeldahl nitrogen (Nk) and a
linear
function of the following biochemical parameters: microbial biomass C,
mineralized
N, phosphomonoesterase, b-glucosidase and urease (Nc). Deviation from
this
equilibrium in minesoils and soils altered by the presence of heavy
metals
or by agricultural use is reflected by deviation of the Nc/Nk ratio
from
100%, and this ratio can therefore be used as an indicator of
biochemical
soil quality.
- Changes in enzyme activities
during the reclamation
of two soils from limestone quarries in Catalonia using high doses of
sewage
sludge. M. Bonmatí, P. Jiménez, H. Álvarez, E.
Calero, M. Julià, M. Morillo and E. Nuñez
Two
field experiments of three and five years duration were performed in
two
limestone quarries (Lucas and Rubau) of different edaphic and climatic
characteristics.
In each quarry a mixture of soil and different quantities of sewage
sludge
were applied to different plots; after addition of the sewage
sludge-soil
mixture, the mean initial total organic C content of the Lucas plots
was
16.9 and 20.3 and 177.6 g/kg (dry matter), and 12.7 and 17.3 g/kg (dry
matter)
for the Rubau plots. In Lucas quarry plots to with only sludge (without
mixing
soil) was added, were also stablished. The mean initial total organic C
content
of these plots was 177.6 g/kg. Plots with no added sludge were used as
controls.
The following enzymatic activities were determined in periodically
taken
samples: phosphatase, urease, invertase, protease,
N-a-benzoyl-L-argininamide
(BAA) hydrolysing, which is specific for trypsin, and casein
hydrolysing,
which is essentially non-specific. In general, the addition of sludge
increased
all the assayed activities in a dose-dependent way, the effect
persisting
until the end of the experiment. The results obtained in Rubau
indicated
that casein-hydrolysing was the most enhanced enzyme activity since it
was
on average six times higher than in the control soil.
N-a-benzoyl-L-argininamide
hydrolysing, protease, phosphatase and invertase activities were also
enhanced
(2.5, 1.5 and 1.5 times respectively), while urease activity did not
differ
statistically from that obtained in the control soil. The enhancing
effect
of the sewage sludge differed depending on the enzyme diminishing with
time
in the case of BAA-hydrolising activity. The was no appreciable change
in
phosphatase activity during the experiment and invertase activity only
diminished
in the last sampling date. Urease activity was only enhanced by the
added
sludge two years after the beginning of the experiment, and this only
in
the case of the mixture with the highest sludge content, although the
effect
disappeared by the last sampling date. It was concluded that the
initial
high ammonium content of sludge inhibited urease activity during the
first
year of the field experiment.
A model was proposed to reflect organic
matter evolution in the five year experiment. According to this model
mineralization
prevailed during the first year, partially counterbalanced by the
priming
effect of soil or the mixtures, and then by the incorporated organic
matter
from plant residues. Mineralisation continued between one and five
years
while organic matter was progressively stabilised.
- Enzymes as a measurement of
environmental impact on soils. M.C. Lobo, I. Sastre and M.A. Vicente
Increased
levels of industrial activity have led to a wider range of potential
soil
pollutants. Soil microorganism activity can help disperse these
pollutants,
accelerating the transfer of toxic matter to the biosphere or
stimulating
bioremediation processes in those pollutants derived from waste
products.
It is therefore interesting to be able to ascertain the microbiological
processes
which take place in the soil system, as well as to understand the role
that
enzymes play in the bioremediation processes. Enzymes are also
potential
indicators of the extent to which soil disturbance by a given activity
may
affect the immediate environment.
This paper analyses the influence of
several types of disturbance (heavy metals, pesticides and soil
degradation)
on the microbiological activity of the soil, focusing on several
enzymatic
activities of particular importance in the nutrient cycles of the
soil-plant
system.
|
Research
and Perspectives of Soil Enzymology in Spain. 2000. Carlos
García & M.
Teresa Hernández (editors). CEBAS-CSIC. Murcia, Spain. I.S.B.N.
84-605-9821-7