Revista Temes Rurals núm. 1

Soil biodiversity
In recent years, soils have been recognized as playing a double
role in the entire agro-ecosystem: it is important for good
production as well as for a healthy environment. Sustainable
agricultural management practices stimulate and select soil
microorganisms such as those involved in the carbon and
nitrogen cycles, and those that promote plant growth and/or
that act as a deterrent against pathogenic microorganisms.
The microorganisms are able to influence the quality of the
soil and the growth of plants, by regulating the availability and
the recycling of nutrients. Soil bacterial communities change
in their structure and dynamics in response to different soil
management practices and can give information about soil status,
in terms of its quality and biological complexity (Ding et
al. 2013). The microbial diversity of the soil is the basis of the
fundamental role played by microorganisms for the functioning
of terrestrial ecosystems. In fact, the greater the degree of
intra or interspecific biodiversity and a functional agricultural
ecosystem, the greater the tolerance of the latter to perturbations
and its resilience (that is the ability to recover following
a disturbance) to unfavourable environmental factors. In bacteria-plant
interactions, both the bacteria and the plant profit
from each other. These interactions play an important role in
agriculture, positively affecting plant status and improving
product quality. Different studies in an olive grove located in
Ferrandina (Matera, Southern Italy) and sustainably managed
for a long period (more than 15 years), revealed positive effects
on soil biodiversity, microbial composition and activity
(Sofo et al., 2013) [Figure 7]. The sustainable olive grove
showed a higher total number of bacteria and microbial complexity,
with a more genetic, functional and metabolic diversity
of soil microorganisms. Supporting culture-dependent results,
metagenomics analysis revealed that a different soil bacterial
composition was detected between the two management systems,
with the sustainable one characterized by the presence
of more microorganisms involved in C and N cycle.
Paisatge i ecosistemes
ST
CT
Fungi
(CFU x 10 4 /g dry soil)
21.4 ± 11.8
2.9 ± 1.9
Bacteria
(CFU x 10 6 /g dry soil)
35.6 ± 16.7 a
10.0 ± 2.6 b
Figure 7: Total bacteria and fungal counts in soils sampled from sustainable and conventional olive groves.
Author: from Sofo et al., 2013.
Nitrogen dynamics and N-cycling bacteria
Under Mediterranean climates, sustainable soil management
aimed at increasing soil organic carbon and microbiological
fertility is of key importance. In conventional agriculture, adopted
by the majority of farmers, frequent soil tillage strongly reduces
the complexity and diversity of soil microbiota. For this
reason, conventional, non-sustainable, agronomic practices
should evolve into a more sustainable management (e.g. grass
cover, pruning residues recycling, organic matter inputs, etc.)
addressed to ameliorate the ecological networks and nutrient
cycling in which soil microorganisms are involved. Agricultural
management practices, such as minimum tillage or no-till,
recycling of locally derived organic matter and adequate irrigation,
fertilizer application and pruning, are required to increase
soil fertility and plant nutritional status. Soil microorganisms’
dynamics (e.g. mobility, growth, nutrient absorption and respiration),
an important part in soil fertility and quality are strongly
affected both by the type of soil management and irrigation
(Jeanbille et al., 2016). On the other hand, the functionality and
metabolism of soil microorganisms are related to soil quality
and fertility, as they influence and at the same time are influenced
by the soil carbon (C) and nitrogen (N) contents, being
bacteria an essential part of C and, even more, of N cycling
processes (De Vries and Shade, 2013). The metabolic and
genetic diversity of soil bacterial communities is affected by
carbon and nitrogen dynamics: the study of the soil N-cycling
bacteria and of the N dynamics could help to understand how
soil management can affect soil status.
In the case of olive orchards, that are a conspicuous part of the
Mediterranean agricultural landscape, defining microbiological
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Fruit orchard management: How can we adapt to/face climate change?