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Soil & Tillage Research
journa l homepage: www.elsevier.com/locate/still
Platy structure development under no-tillage in the northern humid
Pampas of Argentina and its impact on runoff
a, d c a
María Carolina Sasal *, Hubert Boizard , Adrián E. Andriulo , Marcelo G. Wilson , b
Joël Léonard
a
INTA EEA Paraná, Ruta 11, km 12.5 (3101), Oro Verde, Entre Rios, Argentina
b
INRA, UPR 1158 AgroImpact, site de Laon, F-02000 Barenton-Bugny, France
c
INTA EEA Pergamino, Ruta 32 km 5.5 (2700) Buenos Aires, Argentina
d
INRA, UPR 1158 AgroImpact, site d’Estrées-Mons, F-80203 Péronne, France
A R T I C L E I N F O A B S T R A C T
Article history:
Received 28 January 2016 The no-tillage system (NT) is widespread in the silty soils of the Argentine Humid Pampas. The aims of
Received in revised form 17 August 2016 this study were i) to characterize the evolution of the structure of the A horizon in the northern Humid
Accepted 19 August 2016
Pampas due to conversion to NT, particularly the presence of platy structure and its development through
Available online xxx
time, by taking advantage of a chronosequence since conversion to NT; and ii) to evaluate how platy
structure extension in the A horizon relates to characteristics of the crop sequences and runoff in a long-
Keywords:
term experiment. Thus, the structure of the A horizon of 25 Argiudolls with different NT history was
Platy structure
analyzed using a visual structure evaluation (VSE) method (“le profil cultural”). Fourteen natural-rainfall
No-tillage
erosion plots with 3.5% slope were used to analyze the relationship between the soil structural state, the
Runoff
crop sequence and runoff. The VSE method allowed us to understand the structure type organization of
silty soils under NT, highlight the regional extent of a platy structure near the soil surface, and study its
evolution and impact on runoff. All the sites analyzed exhibited a horizontal platy structure (2–10 cm
thick), mainly developing on the soil surface or right under the granular structure on the soil surface.
Under the platy structure, a cF structure was observed in all the sites (30–75% of the A horizon). A
relationship was found between the number of consecutive years under NT and the proportion of platy
structure. This evolution may result from the combination of an initial development of the platy structure
and a late development of a cΓ structure from the soil surface. The results obtained during the five-year
period analyzed allowed us to prove that platy structure alters the drainage pattern, restricts water entry
into the soil and favors surface runoff according to its proportion in the profile of A horizon.
ã 2016 Elsevier B.V. All rights reserved.
1. Introduction grassland, where udic water and thermal temperature regimes
prevail. The most representative soil, and by far the most common
Argentina is among the countries with the largest cropped area in the northern Humid Pampas, is the Typic Argiudoll (Hall et al.,
with continuous cropping under no-till systems (NT). Over the last 1992), with high silt content in the A horizon. In this type of soil,
decades, large changes have taken place in crop sequence the absence of tillage can lead to the formation of massive
composition, toward the disappearance of pastures and the rapid structures (Senigagliesi and y Ferrari, 1993). Generally, soybean
expansion of soybean monoculture (Caride et al., 2012; Wingeyer monocultures under NT, which are harvested during the wettest
et al., 2015). Currently, 19 million hectares of soybean are annually period of the year, are sparsely covered by crop residues and have
sown in Argentina, mainly under NT. poor distribution of the root system, long fallow periods and
The most frequent arable soils of the Humid Pampean region non-controlled traffic, all of which contribute to soil compaction
are Mollisols developed from deep eolian sediments under (Alvarez et al., 2014).
There are specific field observations of a platy soil (P) structure,
with thin and flat fragments oriented parallel to the soil surface,
occurring in the first centimeters of soil in some experiments
* Corresponding author.
E-mail addresses: [email protected], [email protected] (M.C. Sasal). under NT in the Pampas region (Bonel et al., 2005; Sasal et al.,
http://dx.doi.org/10.1016/j.still.2016.08.014
0167-1987/ã 2016 Elsevier B.V. All rights reserved.
Please cite this article in press as: M.C. Sasal, et al., Platy structure development under no-tillage in the northern humid Pampas of Argentina
and its impact on runoff, Soil Tillage Res. (2016), http://dx.doi.org/10.1016/j.still.2016.08.014
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2006; Alvarez et al., 2009). Some authors have also reported 2. Materials and methods
continuous platy structure in silty soils under NT in other areas
(Pagliai et al., 1983; Shipitalo and Protz, 1987; Ball and Robertson, 2.1. Sampling locations to characterize the soil structure by using a VSE
1994; Boizard et al., 2013). In long-term experiments carried out in and its relation with the cropping system
Pergamino, in the center of the Pampas, this platy structure
restricts the water infiltration rate into the soil profile (Sasal et al., The region of the northern Humid Pampas covers about
2
2006). 165,000 km and is located between 31 and 35 S and 58 and