Duval M.E., J.A.
Galantini, J.M. Martinez, F.M. López, L. Wall. 2016. Sensitivity of different
soil quality indicators to assess sustainable land management: Influence of
site features and seasonality. Soil & Tillage Research 159: 9-22.
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The turnover rate of labile organic fractions varies
continuously due to different soil uses and managements, weather conditions and
time of sampling. The aim of this study was to quantify the effect of different
agricultural management, season and soil type on soil organic carbon (SOC) and
its different fractions. The study was conducted on four sites located in the
Argentinean Pampas. In each site, three treatments were defined: Good
Agricultural Practices (GAP), Poor Agricultural Practices (PAP) and Natural
Environment (NE). During two consecutive years (2010 and 2011) and at two
different times (February and September) undisturbed soil samples were taken
at0-20 cm depth. Variables assessed included: SOC and its organic fractions:
coarse and fine particulate organic carbon (POCc and POCf, respectively), SOC
associated with a mineral fraction (MOC), total and soluble carbohydrates (CHt
and CHs, respectively), bulk density, and large pores (P>30). Also, indices
associated with soil and management variables were determined. SOC reductions
caused by agricultural practices were mainly from POCc. This fraction
represented 34-52% and 50-74% for PAP and GAP, respectively, of the observed in
NE. The carbon pool index (CPI) shows that agricultural treatments induced
greater variations in all the labile organic fractions compared with SOC and
MOC. In turn, the magnitude of variability was different among fractions, where
temporal fluctuations increased according to the following order MOC< SOC
<POCf≤CHt<CHs ≤ POCc. Independently of the soil type, the CPI was a
sensitive indicator of soil quality in these systems under no-tillage. The
multivariate analysis has proven to be an efficient analytical methodology for
the identification of soil indicators that respond to agricultural practices,
in which chemical properties (POCf and CHt), physical (BD and P>30), and
indices (SOC:clay, structural index and intensification sequence index) were
the variables that best explained the total variance of information of the four
sites. Therefore, these indicators/indices should be included in any minimum
data set for evaluating the agricultural soil quality under no-tillage in the
studied area.
Keywords: Soil organic carbon; Organic
fractions; Multivariate analysis
Galantini, J.A.; M.
Duval; J.M. Martinez; V. Mora; R. Baigorri & J.M. García-Mina. 2016.
Quality and quantity of organic fractions as affected by soil depth in an
argiudoll under till and no-till systems. International Journal of Plant &
Soil Science 10 (5) - doi:10.9734/IJPSS/2016/25205
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Journal Google Drive
The turnover rate of labile organic fractions varies
continuously due to different soil uses and managements, weather conditions and
time of sampling. The aim of this study was to quantify the effect of different
agricultural management, season and soil type on soil organic carbon (SOC) and
its different fractions. The study was conducted on four sites located in the
Argentinean Pampas. In each site, three treatments were defined: Good
Agricultural Practices (GAP), Poor Agricultural Practices (PAP) and Natural
Environment (NE). During two consecutive years (2010 and 2011) and at two
different times (February and September) undisturbed soil samples were taken
at0-20 cm depth. Variables assessed included: SOC and its organic fractions:
coarse and fine particulate organic carbon (POCc and POCf, respectively), SOC
associated with a mineral fraction (MOC), total and soluble carbohydrates (CHt
and CHs, respectively), bulk density, and large pores (P>30). Also, indices
associated with soil and management variables were determined. SOC reductions
caused by agricultural practices were mainly from POCc. This fraction
represented 34-52% and 50-74% for PAP and GAP, respectively, of the observed in
NE. The carbon pool index (CPI) shows that agricultural treatments induced
greater variations in all the labile organic fractions compared with SOC and
MOC. In turn, the magnitude of variability was different among fractions, where
temporal fluctuations increased according to the following order MOC< SOC
<POCf≤CHt<CHs ≤ POCc. Independently of the soil type, the CPI was a
sensitive indicator of soil quality in these systems under no-tillage. The
multivariate analysis has proven to be an efficient analytical methodology for
the identification of soil indicators that respond to agricultural practices,
in which chemical properties (POCf and CHt), physical (BD and P>30), and
indices (SOC:clay, structural index and intensification sequence index) were
the variables that best explained the total variance of information of the four
sites. Therefore, these indicators/indices should be included in any minimum
data set for evaluating the agricultural soil quality under no-tillage in the
studied area.
Keywords: Soil organic carbon; Organic
fractions; Multivariate analysis
Duval M., J.A.
Galantini, Julia E. Capurro, J.M. Martinez, F.M. López. 2016. Use of different winter
cover crops species in soybean monoculture: effects on soil organic carbon and
its fractions. Soil & Tillage Research
161:95-105 doi:10.1016/j.still.2016.04.006
ISSN: 0167-1987
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Journal Google Drive
The current agricultural production systems in the Pampas Region have
been significantly simplified by cultivating large land areas under no tillage
(NT), where soybean is the predominant crop. These systems with long periods of
fall-winter fallow and poor annual input of carbon (C) into the soil lead to
soil degradation, thereby affecting physical and chemical properties. A 6-year
cover crop study was carried out on a Typic Argiudoll under NT in the south of
Santa Fe, Argentina. Various winter species were used as cover crops: wheat (W),
oat (O), vetch (V), an oat + vetch mixture (O + V) and a control (Ct) treatment
without a cover crop. We examined the influence of cover crops on the following
soil organic C-fractions: coarse particulate organic carbon (POCc), fine
particulate organic carbon (POCf) and mineral-associated organic carbon (MOC)
from 2008 to 2011. Aboveground carbon input by the cover crops was related to
the June to October rainfalls. In general, the W and O treatments supplied a
higher amount of C to the soil; these gramineous species produced 22 and 86%
more biomass than O + V and V. The water cost of including cover crops ranged
from 13 to 93 mm compared with Ct. However, this water-use did not affect
soybean yields. On average, gramineous species (pure stand or mixture) supplied
more than 3.0 Mg C ha−1 year−1 to the soil, whereas V
supplied less than 2.0 Mg C ha−1 year−1. Increase in the mean annual
C-input by residues into the soil (cover crop + soybean) explained most SOC
variation (R2 = 0.61; p < 0.05). This relationship was more
evident with labile soil organic fractions, both for POCc (R2 =
0.91; p < 0.001) and POCc + POCf (R2 = 0.81; p < 0.001). The
stratification ratios of SOC (SI, 0–5:10–20 cm) reflected differences among
treatments, where >2.0 for W; 1.7 for O, O + V and V, and <1.5 for Ct.
Soil physical fractionation by particle size showed that cover crops affected
the most dynamic fraction directly associated with residue input (POCc) at 0–5
and 5–10 cm. At 0–5 cm, the effects were observed in the most transformed
fractions (MOC and POCf) 4 years after the experiment started, whereas at 0–20
cm, differences in the labile fractions (POCc and POCf) were found at the end
of the experiment (6 years). Although C-input by the cover crops fueled
decomposition of labile soil organic fractions, concentration of surface SOC
and its associated fractions (POCc, POCf and MOC) was modified after 6 years.
This effect became noticeable during the third year when the plots under cover
crops showed a higher SI than the traditional fallow.
Keywords
Wheat; Labile fractions; No-tillage
Zalba P., N.M.
Amiotti, J.A. Galantini, S. Pistola. 2016. Soil humic and fulvic acids from
different land use systems evaluated by E4/E6 ratios. Communications in Soil Science
and Plant Analysis 47 (13-14) 1675-1679. Doi 10.1080/00103624.2016.1206558
ISSN: 0010-3624 (Print)
1532-2416 (Online)
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Changes in land-use systems such as the introduction of trees on
agricultural land can give rise to changes in the physicochemical properties of
the soils, also affecting the quantity and quality of organic matter incorporated
into the system. The present study assesses humic substances (HS) in the soil
such as humic acid (HA) and fulvic acid (FA) by looking at the relationship
between the optic densities determined at 465 and 665 nm (E4/E6 ratio). Topsoil
samples (0–20 cm) from pine woodlands 60 years of age were compared with
agricultural soils of similar age in the central-south region of the Province
of Buenos Aires, Argentina. The pH of the topsoil from beneath the pine trees
was highly acidic (5.0 vs. 6.2) and a significant increase in the level of
organic carbon (OC) was registered. The carbon to nitrogen (C/N) ratio was also
higher (by one order of magnitude) beneath the pine trees, although the
humification conditions of the soil organic matter (SOM) were good in the soils
of both studied land-use systems. The E4/E6 ratio was higher in the HA and FA 2
(second extraction) beneath the pines, indicating a smaller molecular size of
the HS bound to the clay minerals. This fact can be attributed to the higher
concentration of hydrogen ions beneath the pines and consequently the loss of
polyvalent cations, mainly calcium. The most labile organic molecules (FA 1 –
first extraction) were of a larger size in soils beneath the pines, most likely
owing to a specific characteristic of the Pinus genus, although the fraction in
question constitutes a minority fraction among the HS. Clear differences were
established between the E4/E6 ratios in HA and FA, making this a highly useful
method for determining molecular changes in HS as a result of changes in land
use.
KEYWORDS: Fulvic acid, humic acid,
pinus afforestation
