Sa Pereira E, J.A.
Galantini, M. Duval. 2017. Use of a three-compartment model to evaluate the dynamics of cover
crop residues. Archives of Agronomy and Soil Science 1-7. doi
10.1080/03650340.2017.1296137
ISSN: 0365-0340 (Print)
1476-3567 (Online)
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Cover crop (CC) residues protect the soil from erosion and their
permanence on the surface is largely influenced by their biochemical
constituents. In this study, the dynamics of CC residue decomposition by
applying mathematical models was described. The kinetics of decomposition of
residues was obtained from a laboratory incubation experiment. Three CC shoot
residues were applied on the soil surface and incubated for 362 days (with
eight sampling times). Oats and vetch residues decomposed the most than clover,
where k values were 3.6 × 10−3, 3.7 × 10−3 and 5.3 × 10−3
day−1, respectively. The three-compartment model (nonstructural
carbohydrates, cellulose–hemicellulose and lignin) to simulate residue
decomposition presented a close fit between simulated and measured data. The
decomposition rate constant (k) of CC can be used to estimate how long residues
will remain in the field and how they could affect soil organic carbon.
Keywords: Residue decomposition;
oats; vetch; clover
Martínez J.M., J.A.
Galantini. 2017.
A rapid chemical method for estimating potentially mineralizable and
particulate organic nitrogen in Mollisols. Communications in Soil Science and
Plant Analysis 48(1) 113-123. doi: 10.1080/00103624.2016.1254230
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The objective of this study was to obtain an indicator of labile
nitrogen (N) through a cost- and time-saving procedure by evaluating the relationships
among potentially mineralizable N (N0), particulate organic matter N
(POM-N) and soil organic N extracted through partial soil digestion with
different concentrations of sulfuric acid (H2SO4). Soil
sampling (0–20 cm) was from nine fields under no-tillage. The N0 and
POM-N were determined by long-term aerobic incubation and soil physical
fractionation, respectively. A simple chemical method was developed by soil
digestion at 100°C for 4 h with different concentrations of H2SO4
(0.1, 0.5, 1, 6, 12, and 24 mol L−1). All acid concentrations showed
significant relationships with N0 as POM-N; however, the best
prediction was resulted for 0.5 mol L−1 (R2 = 0.90–0.94,
respectively), thus using this methodology as soil labile N indicator. This
method would optimize N0 and POM-N estimation in short term and at a
low cost.
Keywords: Chemical digestion; labile organic fractions; no-tillage
Behrends K.F., M.A. Soria,
M.G. Castiglioni, M. Duval, J. Galantini, H. Morrás. Morpho-structural
evaluation of various soils subjected to different use intensity under
no-tillage. Soil & Tillage Research 169: 124-137.
doi:10.1016/j.still.2017.01.013
ISSN: 0167-1987
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According to many evidences, in Argentina, no-tillage (NT) coupled with
soybean monoculture leads to adverse soil structure features. While some
farmers have simplified the production system through soybean monoculture
others have intensified the land-use by increasing the number and diversity in
the crop sequence. The effects of this intensification, in terms of soil
structural quality, are contradictory, possibly caused by the increase of
machinery traffic. In order to assess soil structural quality and the
performance of selected morpho-structural variables with different levels of
intensification, we analyzed plots under NT with high and low crop sequence
intensification (Good −GAP- and Poor −PAP-, agricultural practices
respectively) and reference plots in four soils (two Argiudolls, an Haplustoll
and an Hapludert) of the Argentinian Pampean region. The morpho-structural
variables assessed were Visual Evaluation of Soil Structure at field scale
(VESS), visible porosity (Vp), roundness (Rd), eccentricity (Ecc) and 3-D
aggregate features (faces, corners and edges). Plots with higher frequency of
cereals in the sequence (GAP) presented on average higher VESS scores, higher
Vp values and less rounded aggregates with more faces and corners, suggesting
that crop sequence intensification induces favorable structural features. VESS,
Vp, number of faces and corners were strongly correlated with aggregate
stability tests mainly with the fast and fast10s test (r: −0.56, −0.74; 0.48,
0.52; 0.46, 0.49 and 0.42, 0.50, respectively) and with the more labile organic
carbon fractions −POCc and POCf- (r: −0.49, −0.5; 0.5, ns; 0.38, 0.48 and 0.31,
0.43, respectively). These observations suggest that the variables examined,
concerning aggregates and pores were sensitive to changes in crop sequence and
are useful soil quality indicators. However, the occurrence of platy structures
also under GAP shows the need to adjust the VESS method to the NT system. Besides,
the effect of agricultural intensification on soil morphology was modulated by
soil type. In consequence, this last factor has also to be considered for the
definition of a quality indicator to track the effect of crop sequences
intensification under no-till management.
Keywords: Aggregate morphology;
Image analyses; VESS
Martínez J.M., J.A.
Galantini., M Duval. 2017. Tillage effects on labile pools of soil organic nitrogen in a
semi-humid climate of Argentina: A long-term field study. Soil & Tillage
Research 169:71-80. DOI 10.1016/j.still.2017.02.001
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Tillage systems strongly affect nitrogen (N) mineralization. However,
there is still only limited information on the relationship between N in labile
soil organic matter (SOM) fractions and crop N uptake under different tillage
systems in areas with poor water availability. This study discusses the
long-term effect of two tillage systems on i) the N-content in labile organic
matter fractions and their relationship with the N mineralization potential at
three depths (0–5; 0–10 and 0–20 cm), ii) the factors that affect the N
mineralization potential, and iii) the relationship between potentially
mineralizable N (N0) and crop N uptake in a semi-humid climate. In a long-term
experiment, a Typic Argiudoll was sampled under two contrasting tillage
systems: no-tillage (NT) and conventional tillage (CT). The soil sampling was
performed over four years of the crop sequence (2003, 2009, 2010 and 2011) when
the plots were sown with winter wheat (Triticum aestivum L.). They were
analyzed for N0 in the form of anaerobic N, soil organic nitrogen (SON),
physically separated SOM fractions and crop N uptake. Higher values of SON and
labile soil N fractions were observed under NT at all three depths. Significant
differences in N0 were found between the tillage systems, with greater values
under NT. Significant (P < 0.05) and positive correlations between N0 and
fine particulate organic carbon (fPOM-C) (r ≥ 0.66) were found in CT and in NT
at the three depths, whereas highly significant (P < 0.001) and negative
relationships between N0 and fine particulate organic N (fPOM-N) (r ≥ −0.83)
were found under both tillage systems at 0–5 and 0–10 cm. The most pronounced
difference in these relationships between tillage systems was observed at the
0–5 cm soil depth. Significant correlations of N0 with residue input from
previous crops and the fallow period were observed under both tillage systems
and for all three depths. Regarding the relationships between N0 and wheat N
uptake, no significant correlations were found for any tillage system or depth.
Soil organic N fractions were shown to be strongly influenced by the residue
input from the previous crop and by variable weather conditions during the
fallow period. The higher content of SON fractions under NT was associated with
a higher N mineralization potential, however, it did not result in increased N
availability and N uptake by wheat, because of climatic conditions during the
crop growing season.
Keywords: Potentially mineralizable
N; Soil labile fractions; Tillage systems
Vanzolini J.I., J.A.
Galantini, J.M. Martínez, L. Suñer. 2017. Changes in soil pH and phosphorus
availability during decomposition of cover crop residues. Archives of Agronomy
and Soil Science 63 () http://dx.doi.org/10.1080/03650340.2017.1308493
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The aim of this study was to
determine the effect of winter cover crop (CC) residues on soil pH and phosphorus
(P) availability. Three incubation assays were performed in pots using two CC:
vetch (V) (Vicia villosa Roth.) and
oats (Oa) (Avena sativa L.). Soil
samples were taken from 10 sites at 0–20-cm depth. The rate of residues were 0
(D0), 10 (D1), 20 (D2), 30 (D3), and 40 (D4) g dry matter kg−1 soil
and the soil sampling was after 10, 20, 30, 60, 90, and 120 days of incubation.
Soil pH, extractable P (Pe), and soil organic matter (SOM) and its fractions
were determined. The pH increase was correlated with the rate applied (D1 <
D2 < D3 < D4). No differences were found for pH comparing V and Oa
residues with low residue rates. Soil pH changes were dependent from initial pH
and SOM fractions in different soils across the incubation period. The multiple
regression models showed that the pH changes were dependent on initial pH level
and SOM fractions with a high R2 (0.81). CC residues and its
quantities produced different changes on pH – especially at the beginning of
the incubation – which influenced the P availability.
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