Authored by Eduardo Jose Azevedo Correa,
Arbuscular mycorrhizal fungi (AMF) are commonly present in most
tropical land ecosystems; however, high rates of fertilization can
disrupt
their life cycle. The AMF occurrence in different crop systems compared
to native vegetation in tropical conditions is not well understood. With
the aim to analyze potentially benefic symbionts for crop production in
an experimental farm, the AMF community structure along different crop
cultivation was investigated. Soil subsamples were used to inoculate
trap cultures using Sorghum sp. as host. The preserved unfertilized area
showed
a greater diversity of AMF, followed by the grassland and sugarcane.
Number of AMF spores was also greater in the preserved area (47 spores
per
100g soil) than the numbers estimated for other sites. Nine AMF genera
of Glomeromycotina (spores) and 16 AMF species were observed in the
native forest. The natural richness appears to be favored when Sugarcane
or grasses are planted; however, the preserved native forest showed
unique characteristics. Soils under native forest stored higher amount
of SOM, presented higher macro-aggregates and preserved more charcoal
than the samples of permanent grassland or under maize. The maize
associated AMF community diverged from grassland, as described by the
principal component analysis. This study showed differences in AMF
communities from cultivated plots compared to native vegetation as well
as
potential for inoculant formulation for economically crops.
It is known that land-use intensification affects multiple ecosystem
services mainly by plant biodiversity loss [1], together with
suppression of rhizospheric plant symbionts. Among plant-soil microbiota,
the arbuscular mycorrhizal fungi (AMF) have common occurrence.
However, some plant species do not perform symbioses
with that fungi), differently that most agronomic species [2]. Nevertheless,
the use of fertilizers and the type of plant-soil management
can affect the occurrence and diversity of AMF species compared
with preserved areas [3]. Increasingly reports on maize showed
higher AMF richness under optimized N input agro-systems [4].
Moreover, chemical fungicides can also affect root colonization
by AMF as well as the number of spores [5]. Fertilization regimes
have impacts on maize root-associated AMF community [6]. Recent
reports showed that oxisoil Al saturation present in Brazilian tropical
soils can change the AMF richness in maize roots [7].
Soil aggregation is sensitive to changes in management practices
[8], in soil compaction and in plant and edaphic animal populations
[9].
The morphological spore identification can provide a more
sensitive detection of changes in AMF community composition and
diversity in fields than molecular methods [10], as detected in some
analysis carried out under temperate climate in plots subjected to
intensive agriculture and no-till treatments that showed negative
effects of tillage for AMF diversity [11].
Opik et al. [12] compiled information on number of AMF taxa
and showed significantly higher richness in tropical forests, followed
by grasslands and cultivated areas. The AMF occurrence in
different crop systems compared to native vegetation in tropical
regions such as in Brazil was not well investigated. In Brazil, the
Atlantic Forest biome contribute to multiple environmental functions;
however, the original area was extremely reduced, resulting
in immediate conservation measures. Most reports showed that
conversion of Atlantic Forest into pasture changes the biological
properties and dynamics of SOM [13].
The Atlantic Forest in Southeastern Brazil is found in small
fragments in the Meso-region of Belo Horizonte, Minas Gerais State,
where plant species from Atlantic Forest and Cerrado Brazilian
biomes, both considered as hotspots of biodiversity [14], occur.
Atlantic forest total sampled area represents simply 0.01 % of the
remaining biome, Minas Gerais state being one of the better studied
[15]. However, most landscapes save for conservation purposes
(marginal agricultural lands) can hold high species diversity providing
biodiversity conservation services [16]. Thus, to improve
the conservation of anthropogenic landscapes in Brazilian tropical
forest is urgently needed [17].
With the aim to analyze AMF potentially benefic for crop production
in experimental farms, we show in the present study, results
of estimates of AMF communities’ structure along one year
of crop cultivation. The Experimental farm in Pitangui (an area of
460ha) includes preserved riparian areas between São João and
Pará Rivers, localized in the São Francisco River basin, a protected
Reserve (its vegetation is primarily Atlantic Forest), forestry, and
corn/sugarcane fields. Experimental farm belongs to EPAMIG ITAC
Company (Empresa de Pesquisa Agropecuária de Minas Gerais),
located in the center-west region of the state of Minas Gerais and
dedicated to research with regional cultivars potentially important
for intensive systems of production or screening programs. Plant
crops are rice, corn, beans, soybean, to name just a few.
Four different areas were studied from maize and sugarcane
monocropping, grassland to environmentally protected Native Forest.
Among cultivated pastures, Brachiaria grasslands (B. decumbens
and B. brizantha) are the most important agronomic species in
Brazil, also used for Integrated Crop-Livestock-Forest systems [18].
The grassland for pasture (Brachiaria brizantha), the continuous
maize monocropping with high input of fertilizers and pesticides,
and sugarcane monoculture (Saccharum officinarum) fertilized
only with compost were selected.
We hypothesized that soil grassland could contain high AMF
spore numbers, macroaggregates and charcoal, but the native forest
can present the highest values. Furthermore, we hypothesized
that changes in land-use affect the fertility and structure of the soil
matrix so that the overall. We predict monocultures to impact the
AMF community in this study. Studies investigating AMF diversity
in tropical native forest, grassland and crop fields are scarce, but no
available studies have been targeted to the anthropogenic disturbances
that drive AMF community shifts together with soil aggregation
and charcoal content.
The aims of this study were: (1) to evaluate the communities
of AMF in different ecosystems of land use intensity from undisturbed
preserved and permanent grassland to monocultures, (2)
to associate the AMF communities with soil characteristics and (3)
to evaluate the effect of inoculation of soil containing arbuscular
mycorrhizal propagules on plant growth, as part of a greenhouse
experiment. Since we wanted to focus on the simple on farm inoculation
(mixed AMF spores in soil) alone, we chose to compare different
non-sterilized soils.
Field analysis
Study sites. The four sites (Table 1) selected for this study are
located in the plain of the São Francisco River basin located in Brazil.
Four land use types, e.g. maize field (19°42’48.1”S, 44°53’45.3”W),
grassland (19°42’51.5”S, 44°53’37.0”W), sugarcane (19°42’40.9”S
44°53’40.0”W) and Atlantic forest (19°42’49.9”S 44°54’07.8”W.)
(Representative of land use with different intensity in descending
order), were selected as sampling sites.
Different areas were sampled:
1. Native Forest (NF), nature reserve about 25m from São
João River, presenting Atlantic forest cover (80ha). The Forest
Reserve is a protected area of Atlantic forest with prominent
vegetation composed by trees and shrubs having a total density
of ~1,029 trees per hectare reaching heights of 10–25m [19].
Dominant species are listed in Table 2. Plant vegetation had
been undisturbed for 30 years. Some plant species are at risk of
extinction such as Cariniana legalis. Exsiccates were deposited
in Herbarium PAMG of EPAMIG;
2. The Grassland (G) has gramineous cover with Urochloa
brizantha syn. Brachiaria brizantha Stapf under no-till cultivation
being the dominant grass; (about 1000m from São João
River). The G is located in the direct neighborhood of Maize;
3. Maize (M) monocropping (Zea mays cultivar AG1051)
(conventional hybrid for silage) area, 5ha, fertilized with 400kg
8:28:16 NPK and 350Kg urea; Maize were planted in late January
and harvested in December each year from 2004 to 2014.
Last maize cultivation was in the year 2014. The maize was
manually sowed on December 2014. Assessments of soils were
made after the maize harvest, between August 2015 and October
2015. Weeds and pests, when they appeared, were treated
with insecticide Klorpan 480 CE (three applications); Herbicides
SANSON 40 SC and DMA 806 BR (one application);
4. Sugarcane (S) (0.7ha) Saccharum officinarum variety
melifera melifera 418, cultivated under undetermined compost,
harvested and crushed to feed livestock. This site was only evaluated
in the second sample period (Table 2).
All the sites have the same geological parent material and were
classified as clayey Oxisol (Typic Acrustox) according to Soil Taxonomy
[USDA 1992]. The cultivated soils are loamy (Figure 1).
The climate of the region is Tropical (Aw) with an annual average
temperature of about 23 °C and predominant precipitation in
summer and dry winter. This area was characterized by a total solar
radiation of 7.2h, an average precipitation of 1337mm per year.
The study area is located in the west of Minas Gerais State, in
Brazil, included in the Cerrado- Atlantic Forest region (19°40´ S
44°53´ W), characterized by 709mm of yearly precipitation concentrated
in the spring-summer months from November to January
(Meteorological station Mineração Turmalina, Jaguar Mining
Inc. (19°44’36” S, 44°52’36” W, 700m), located 6 km south of the
town of Pitangui. Near 84% of tropical rainfall falls during the rainy
season (October to March). The months of December and January
present the most intense precipitation levels. Air humidity, even in
the summer, does not exceed 86% on average (Figure 2).
Brief land-use history
The original vegetation of the area is derived from Atlantic forest/
Brazilian Cerrado ecotone, although part of the forest was deforested
as early as the 1970s as revealed by interviews with local
farmers. The area comprises the São João River with approximately
5m width and 1 to 1.5m deep. The São João basin vegetation was
partially degraded and substituted by grasslands or eucalypt plantations.
The experimental farm in Pitangui has been divided into eight
sectors: cultivated areas, zootechny in general and Forest reserve,
dedicated to research with regional cultivars potentially important
for intensive systems of production or screening programs such as
rice, corn, beans, soybean, to name just a few. In the 1970s, this area
was donated to the Minas Gerais State.
Typical land-use types in the area include forestry, cornfields,
sugarcane plantations and grasslands. The agricultural use of the
soils includes planted grassland (G); arable lands with moderate-intensity
management, such as maize and sugarcane monocropping
(M, S) (Table 1). The M site was established in 2004, followed by
many years of annual crops. Last maize cultivation was in the year
2014 when it was manually sowed on December. The G site (in the
central area, Figure 1) had been cultivated and then abandoned and
left for grassland, chopped up once a year.
Soil sampling and chemical characterization
Soil samples (three replicate plots per field site; plot sizes, 5
by 20m) were obtained in February (rainy period) and November
(after the dry period) 2015 at four sites.
At each of the three plots at each field site, five soil core samples
were taken up to a depth of 20cm with a mattock, with the exclusion
of the top soil layer (0–5cm), totalizing 30 samples. Samples
were stored in plastic bags and transported to the laboratory of
EPAMIG. Each composite sample was air dried and carefully conditioned.
Each sample was stored in bags, and subsequently brought
to the laboratory for analysis. Prior to further processing all visible
roots and rocks were removed manually.
About 500g were used to determination of chemical soil parameters,
according to EMBRAPA (1997). The rest of soil samples was
used for AMF spore extraction and identification. Chemical properties
of the soil determined by the traditional methods as described
by EMBRAPA (1997). The following chemical analyses were performed:
pH in water (1:2.5 soil/water); soil organic carbon (SOC);
P, K+, Ca2+, Mg2+ and Al3+ were determined according to EMBRAPA,
1997) (Table 3).
AMF spore isolation and identification
Wet sieving and sucrose density gradient centrifugation [20]
extracted AMF spores occurring in the original soil samples (50g
soil). The resulting supernatant was passed through the 32-μm sieve, washed with tap water, and transferred to Petri dishes. AMF
communities in each area were recorded and their diversity was
estimated.
Spores and sporocarps were counted by using a dissecting
microscope and mounted on slides with polyvinyl-lactic acid-glycerol
and mixed 1:1 (vol/vol) with Melzer’s reagent. Only the
healthy-looking spores were mounted. The spores were examined
under a microscope, mounted on slides and identified to the species
level or attributed to a specific morphospecies. Identifications were
based on current species descriptions.
The old and decaying spores with missing clear features were
also counted as an approach for comparison among samples [21].
The results expressed as percentage of unviable AMF spores in the
sample. Darkest black color spores or remained damaged were
considered as non-viable. Unviable spore counting was done at 40×
magnification (Figure 3).
Greenhouse analysis
Plant cultures (pots, 20 x 20 x 30cm) were produced for each
site. Seeds of Sorghum BR were planted in pots filled with 3 Kg
of washed sand, vermiculite and collected soils at each field site:
Sugarcane, grassland and Native forest, (1:1:1 [wt/wt]) according
to Oehl et al. [10] a methodology denominated Culture Trap, were
plant is the host of Fungi symbiont and promoted his growth in soil
culture.
The greenhouse experiment was initiated in August 2015 and
was maintained in a greenhouse in Pitangui for 3 months under
day/light regimes of 12-h: 12-h photoperiod and 28:25 °C temperature,
with a mean relative humidity of 65%. Seedlings were
irrigated with tap water and plant height were measured at 2 and 3
months after planting (Figure 4).
Statistical analysis
The significance of differences between field sites in spore
abundance, species numbers, and AMF diversity (Shannon-Weaver
index) was tested by using ANOVA one-way. Homoscedasticity and
data normality were tested before performing analysis of variance
and test of means. Tukey post-hoc tests were used to conduct pairwise
tests for significant effects. Associated means for each treatment
were reported using the software Minitab 17 [9].
AMF occurrence
AMF spores were counted and identified for samples taken directly
from field sites. Identification of AM fungal species based on
morphological features of spores in the root zone of maize, sugarcane,
grassland and native forest showed 16 identifiable AMF species.
One species of Glomus, one of Sclerocystis, one of Clareidoglomus,
one of Ambispora, four of Acaulospora, one of Gigaspora and
four of Scutellospora were detected. Four spore types could not be
readily distinguished at the species level.
Table 4: AMF fungal genera found in the different sampled soils. Atlantic
forest (AF), grassland (G) and cultivated (M and S).
In the soil samples taken from the studied systems, 16 AMF
species could be distinguished. The 10 AMF species observed in soil
sampled in the dry and rainy season consisted of seven families and
ten genera (Table 4). Four species belonged to the genera Acaulospora
while the genera Claroideoglomus, Gigaspora, Scutellospora,
Dentiscutata and Ambispora were represented by a single species
each. The species Dentiscutata heterogama, was observed in all the areas, in both the dry and rainy season, the last species being the
most frequent (100 %). The species Sclerocystis rubiforme, Sclerocystis
taiwanensis and Racocetra verrucosa were exclusive to the NF
area, whereas Gigaspora margarita was observed only in the cultivated/
sugarcane areas (Table 4). Glomus sp. 3 was unique to NF and
A. mellea, A. scrobiculata and A. appendicula were shared between
NF and Sugarcane (Figure 5).
Spore numbers
AMF spore numbers in the soil samples ranged from 1 to 23
spores per 100g of soil, with an average of 8 to 12 spores, and significant
differences were detected between sites (Table 5). The
spore numbers in the maize field was significantly lower in the
rainy period than in the NF, G and S. The spore numbers in the NF
(dry period), G, S and Maize field (dry period) were not significantly
different.
Table 5: Total AMF spore numbers (50g soil) of each family in soils from
Natural forest (NF), grassland (G) and cultivated (M and S) (n = 3).
Species richness and diversity
In both seasons, the values of total species richness (S) and the
Shannon diversity index were different among the areas (Table 6),
indicating different composition of AMF communities, ranging from
0.33 to 2.12. In the dry season, the AMF community had greater
similarity between sugarcane and native forest areas, while in the
rainy season, the AMF community of the NF had greater richness.
Table 6: Richness (S), Shannon-Weaver (Hs), Simpson (D) and Evenness
(E) indices calculated from AMF associated with each soil at experimental
farm at rainy and dry periods.
The species numbers in the grassland was slightly, but significantly
lower in the rainy than in the dry period despite the fact that
the similar precipitation had been registered, but more humidity
was detected in the rainy period.
The species richness in the maize fields was slightly, but significantly
lower in the both sampling periods. This analysis indicated
that the different AMF communities with plant cover of grassland/
cultivated samples did not associate with the native fertile soil (Table
7).
Greenhouse experiment
The results of the greenhouse experiment showed higher
growth of Sorghum inoculated with soil from the native forest and
from the grassland sites (Figure 4) than with soil from the cultivated
area. Sorghum height in greenhouse experiment at 2 and 3
months after cultivation was significantly higher by the use of inoculum
from NF and G sites (Figure 6,7,8 & 9).
Our study provide support for the hypothesis that AMF communities
are limited in their diversity by monocultures. We found that
preserved ecosystem (Atlantic Forest ecotone) was more diverse
than agroecosystems, not only in plant diversity but also in AMF
diversity and in improved soil OC content and soil aggregation.
The cultivated soils presented high fertility, a higher pH value,
and lower organic matter content than native forest soil, which presented
moderate fertility and low P and K levels. This shows that
agriculture as practiced in tropical agro-systems for Brazil, negatively
affects the satisfactory nutrient levels (with excess of Ca, K,
P and Mg), increases pH and decrease OM in top soils. Consistent
supplies of fertilizers and lime are required in naturally acid soils
(high contents of aluminum and iron oxides, low CEC values and
OM content) in Cerrado [22].
For P applications in Brazilian crop production systems, soil
test P methods indicate that quantity of plant-available soil P [23]
and the required fertilizer level is then inferred. However, the loss
of fertilizers in agricultural runoff from soils (negative impacts of
Brazilian agriculture) can be controlled via use of conservation tillage,
cover crops, buffer or riparian zones [23], and conservation/
augmentation of biofertilizers/soil conditioners [24].
The proportion of aggregates >2 mm in the investigated soils
slightly decreases in the following order: NF and G > crop. However,
microaggregates were significantly lower in forest soils than in G
and cropland. Similar results from Portella et al. (2012) [8] reported
that macroaggregates are sensitive to changes in management
practices and, from Blanco-Canqui and Lal (2004) [24] reported
some variation in microaggregates. It is also known that water-stable
aggregates >0.25 mm together with soil OM content can significantly
control erodibility [27]. Moreover, the tillage practices
adopted in croplands can disrupt soil aggregates [9], increase soil
compaction and disturb plant and animal populations that contribute
to soil aggregation.
A higher hyphal length, root colonization by AMF and AMF
(spore) species diversity is expected in native forest than cultivated
sites, due to a permanent plant cover, higher soil OM content and
soil humidity [27]. Thus, the higher macroaggregates content under
NF in rainy period can be due to a higher hyphal growth. Soils under
permanent grassland can also store higher soil OM in larger aggregates
than samples under permanent maize [9].
The observed higher quantity of macroscopic charcoal in sugarcane
and NF than in grassland and maize was consistent with results
by Schneider et al. (2011) [28] showing unchanged charcoal
chemical quality and stocks along 100 years in a tropical ecosystem
in western Kenya. The notable increase of charcoal in the sugarcane site
suggesting fire activity maybe by burning management in a previous
period.
Indeed, results showed that each site correlate with distinct
soil attributes. NF associated with OC, charcoal, and macroaggregates.
Thus, soil chemical properties such as Al, Ca, Mg, P and K concentrations
of soil C, and soil aggregates are the main soil factors
distinguishing sites. This study evaluated the AMF communities in
different sampling sites showing that spores belonging to 9 genera
of Glomeromycotina were detected. The results showed that preserved
ecosystem (Atlantic Forest) was more diverse than agroecosystems,
wherein pH is higher, and higher levels of Ca, P and K were
detected.
In general, spore-based morphological studies demonstrated
that application of fertilizers, pesticides, and fungicides results
in significant loss of AMF diversity in many ecosystems [29]. We
predicted that spore-based morphological studies could detect the
occurrence of Gigasporaceae and Scutellosporaceae in more preserved
areas (two species of Racocetra and one of Scutellospora
were found). The total number of AMF species varied among the
evaluated areas being higher in preserved area of Atlantic Forest
(NF), observing that number of AMF spores in preserved area
ranged from 9 to 47 spores in 50 g soil.
In both seasons, the values of total species richness (S) and the
Shannon diversity index were different among the areas, indicating
different composition of AMF communities. In dry season, the AMF
community had greater similarity between sugarcane and forest
areas, while in rainy season, the AMF community of NF had greater
richness. This pattern suggests that AMF community is affected not
only by the host, but also by climatic conditions, and possibly by
soil conditions [30]. Azevedo et al. (2014) [31] also found a high
number of AMF species (37) in a small area of sugarcane plantations.
Aidar et al. (2004) [32] found that H (from 1.10 to 1.96) late
successional preserved Atlantic forest at Alto Ribeira State Park in
Sao Paulo.
The S, where the plant protection strategy is non-burning management
and compost addition, resembled more the G than the conventional
M. The successional dynamics described here are in line
with Whittaker’s (1972). The species numbers in crop fields and
grassland was slightly, but significantly lower in the conventional
than in organic treatments despite the fact that same crop rotation
had been applied. The species richness in crop fields and grassland
was slightly, but significantly lower in the conventional than organic
treatments despite the fact that the same crop rotation had been
applied. This result was confirmed in the trap cultures.
This study agrees with Oehl et al. [10] who also found a decrease
of spore abundance of AMF species not belonging to the
genus Glomus in Monocultures. Many of these species appeared to
prefer or even to be restricted to forest systems. This was the case
for most species of Acaulospora identified from field as well as for
Acaulospora sp. and Entrophospora infrequens. A previous study
indicated a trend towards an increase in AMF belonging to genera
Acaulospora, Scutellospora and Entrophospora under long-term reduced
tillage managements [33].
Our study complements this finding, indicating that not only
reduced tillage but also organic farming may increase the diversity
of AMF species and genera in arable lands. Our findings indicate
that some AMF species, especially Acaulospora spp., find an ecological
niche in soils of organic farming systems, and that this may be
connected with characteristically low level of readily available P in
these soils [10]. We hypothesize that these AMF species are functionally
important to natural ecosystems and low-input sustainable
farming; if this is true, their loss under conventional farming would
be alarming.
The reduced AM fungal diversity in annual croplands compared
to grasslands corresponds with some other studies in tropical regions
[10] and supports the reported inverse relationship between
agricultural land use intensity and AM fungal diversity [10]. The
number of spores in cultivated area was much lower. This spore
distribution points to hypothesis of greater sporulation of AMF detected
in more preserved areas.
Unviable AMF spore number in soil samples ranged from 5 to
62 spores per 100g of soil. The average spores number agree with
the proportion of viable spores, in surface soil, from 35 to 60% detected
by the MTT test [21,34]. In the present study, the proportion
of unviable spores in NF was lower but not significant than in the
other sites, with a possible stable spore production and loss from
spore bank.
Sporulation and dormancy are of prime importance for the
long-term persistence and survival of AMF in any habitat. The AMF
spore bank in soil (formation of new spores and removal from the
bank by death and by germination) will determine the spore numbers
in soils [10]. AMF species differ in their sporulation and germination
dynamics [10].
Sorghum growth experiment at 2 and 3 months after cultivation
was significantly higher by use of inoculum from NF and G
sites. This can be due to different propagules that can be present
in NF and G such as hyphae and spores, corroborating a great bank
of propagules. The finding of higher AMF diversity and plant infection
potential in organic as compared to conventional treatments
fits well with previous observations of a higher soil aggregate
stability. AM inoculation in combination with biochar application
may be applicable not only for maize production but also for Phyto
stabilization of Cd-contaminated soil [35]. Dai et al. [36] AM fungal
resources of soils being resilient to disturbance and that richness
of AM fungi under cropland management has been maintained, despite
evidence of a structural shift imposed by this type of land use.
Roadsides in prairie are a good repository for conservation of AM
fungal diversity.
AMF colonization of sugarcane roots in current study is within
the range observed in other studies, i.e. 10 to 89% in sugarcane
under different field and greenhouse conditions [37-39]. However,
no-burning management resulted in higher root colonization after
the first harvest, as compared to pre-harvest burning management.
Possible explanations for these results are: (I) an enhanced degradation
of the litter driven by the tillage, and (II) more abundant
organ mineral interactions preserving SOM from degradation and driven by the higher root density under grassland. Lignin balance
showed that lignin stocks were more efficiently preserved under
ley and permanent grassland than under permanently cropped
soils.
AMF spores were counted and identified for sample taken directly
from field sites. Identification of AM fungal species basing on
morphological features of spores in rhizosphere soil of maize, sugarcane
and native and restored forest.
In both seasons, the values of total SR and the Margalef diversity
index were very similar among the areas, indicating similar composition
of AMF communities, ranging from 50 to 66 %. In the dry
season, the AMF community had greater similarity between pasture
and forest areas, while in the rainy season, the AMF community
of the regeneration area had greater similarity to that of forest
fragment. This pattern suggests that AMF community is affected
not only by host, but also by climatic conditions, and possibly by
soil conditions [30].
The species numbers in crop fields and grassland was slightly,
but significantly lower in conventional than in organic treatments
despite the fact that same crop rotation had been applied. This result
was confirmed in trap cultures. In this way, the present study
demonstrated the importance of symbiosis with AMF in preserved
areas as potential for the establishment of AMF inoculants for species
of economic interest typical of region.
The inoculum potential of soil samples from the different treatments
in field trial was determined in AMF trap cultures by measuring
the proportion of root length of trap plants after 2 months of
culture. It was found to be highest in the decreased samples from in
same order as the spore abundances observed.
The benefits of AMF to their host plants could not be explained
by improved nutrition alone, since interaction with the remaining
soil organisms (i.e., priming effect of mycorrhiza) also differed
between inoculated AMF. Due to distinct socialization strategies
between inoculated AMF and remainder soil microbes and fauna,
inoculation with irregulars and especially with Scutellospora sp.
did not overrule the soil’s legacy from maize monocropping (and
thus the negative feedbacks), while inoculation with C. claroideum,
F. mosseae and Gigaspora sp. Did [40].
The soil management adopted in cultivated areas decreases the
density and diversity of AMF spores in relation to adjacent natural
vegetation. The present analysis of the surface profile of soils revealed
that Sugarcane cultivation leads to significant accumulation
of charcoal. Sugarcane showed most benefic than maize cultivation
systems. The most accumulation processes occurred in reclaimed
soils, which is due to input and mineralization of plant residues and
soil amendments [41].
The best strategy for reclaimed the degraded cultivable soils
could be to add AMF inoculum better than abandoning cropland
for succession, as unviable spores and lower spore abundances
are present. Thus, soil content can indicate more closely related to
natural soils attributes, when soil. Soil inoculation with propagules of
AMF positively influenced the plant height grown in the greenhouse.
These results demonstrated good prospects for study of functional
diversity of mycorrhizae to attain greater productivity of
regional agricultural systems. Stimulates more effective and ambitious
conservation actions in the region to address the increasing
human pressure and demand for agricultural land expected in coming
decades.
We highlight the need of introduction or maintenance of AMF
spore bank in soil for agronomic management practices. Recommendations
are made for AM functional groups, such as to maintain
preserved forest on rural farm as a source of ecosystem services,
which can be the dispersal of AMF propagules and for use in the
transition of conventional agriculture to organic.
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