This work is a ‘historical’
revision of the evolution of an experimental procedure developed by Prof.
Lisardo Nez and his research group TERBIPROMAT to study the
sustainability and the soil health state.
From the very beginning,
in 1993, the microbial activity was the main bioindicator selected to analyse
the ‘soil health state’. For this reason, a microcalorimetric
technique was used lately to analyse the influence of different human activities
such as reforestations, agricultural exploitation or pollution on the microbial
activity in different soils. Microcalorimetry is the main scientific technique
used in this research to follow the stimulation of the microbial activity
by addition of glucose. The data obtained were complemented by a study of
physical, chemical and biological parameters of soil and allowed to follow
the microbial activity in soils of Galicia (Spain) along the year.
The final results, still in revision, will be helpful in establishing
a data basis for real maps of the ‘health state’ of different
soils. Such maps could be used to design processes that help us to decide
how we should exploit soils ensuring their sustainability.
Summary Soil productivity and health were analyzed using an experimental procedure designed for this kind of studies. The continuous loss of fertile soil obliged the Food and Agriculture Organization (FAO) to declare soil as an item to be protected as a support of the world society welfare. The procedure here described is in accordance with the premises necessary for a rational and sustainable development of soil and the resources it contains and can be used to study any soil all over the world. The study was carried out using soil microbial population as a bioindicator of soil health. Microbial activity was followed using the microcalorimetric technique. The microcalorimetric study can be complemented through a deep analysis of soil physical, chemical and biological properties together with a study of the environmental properties that have a strong influence on the afore mentioned properties and, thus on the microbial activity in soil. The different properties follow different ASTM, ISS/FAO, USDA, etc. well defined standards. The experimental procedure reported in this work could be very helpful to create a data basis that could be useful to quantify and control soil potentiality or design soil decontamination and recovery systems.
Microcalorimetry was used
to study the seasonal evolution over one year of the microbial activity in
a humic-eutrophic Cambisol soil as a function of its forest cover. The study
was carried out on three soils with identical origin but covered with different
forest species: pine, eucalyptus, and a typical Atlantic-humid riverside forest.
Some other physical, chemical and biological
properties and environmental parameters, mainly humidity and environmental
temperature, were considered to analyze their influence on soil microbial
The study was performed using a microcalorimeter Thermal
Analysis Monitor 2277 in which the experiments were carried out with 1 g soil
samples treated with 1.25 mg glucose g–1
soil. From the measured results it follows that pine forest soil is the least
productive of the three, as it generates an average heat of 2.7 vs. 5.9 J g–1 generated
by the eucalyptus forest soil and 3.1 J g–1
generated by the riverside forest soil. These results are dependent on the
remaining physical, chemical and biological features analysed and because
of this, pine forest soil, with a pH value 3.3 in spring, shows a small capacity
to maintain a stable microbial population which is the lowest of the three
(0.079108 to 0.46108
microorganisms g–1 soil) while riverside
soil microbial population is in the range from 7.9108
to 17108 microorganisms g–1
The design of a rigorous experimental procedure is
the basis for any environmental study. In this work, the basic criteria are
established for determination of soil health using microcalorimetry as the
main technique complemented by the study of physical (temperature, moisture,
porosity, hydraulic conductivity, density and plasticity), chemical (pH and
C to N ratio) and biological features (most probable number of microorganisms
and organic matter content), and also environmental properties in the form
of bioclimatic diagrams. The design was elaborated using as a reference a
humic eutrophic-Cambisol subjected to afforestation with P.
pinaster Aiton situated in Viveiro (Galicia, NW Spain). Main results
of this study refer to total heat evolved during the processes (2.65 to 3.81
J g–1), time to reach the maximum of the
peak from 16.17 to 19.29 h, and microbial growth rate constant from 0.0732
to 0.1043 h–1. These results change over
the year as they are influenced by the action of environmental parameters
over soil microbial activity. The results are in close agreement with some
others previously reported using different experimental techniques.
Isothermal and Differential Scanning Calorimetry is applied to analyze the evolution of soil using its microorganisms and
organic matter as bioindicators of soil quality. This study was carried out with two similar soils under different agricultural
activities: culture and pasture. Sampling and measurements were performed through 1 year in order to check the sensitivity
of common calorimetric indicators of microbial activity and organic matter to the different climatic seasons in the sampling
place: spring, summer, fall and winter. Results show that these indicators are sensitive to changes related to climatic conditions
but the variability depended also on the nature of the soil: pasture or agricultural land. The results achieved through the
present study show that the procedure here proposed could be used on any soil everywhere, providing the determination of the
own parameters of soil and zones.