Persistent effects of subsoil compaction on pore size distribution and gas transport in a loamy soil
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Soil & Tillage Research 122 (2012) 4251
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Soil & Tillag
In recent decades, the weight of agricultural machines hasincreased in order to meet the demands of modern agriculture.This ever-increasing weight of agricultural machines causes stresspenetration to deeper soil layers (Carpenter et al., 1985; Kelleret al., 2007; Lamande et al., 2007; Lamande and Schjnning, 2011;Zink et al., 2010) which may result in compaction at greater depthsthan reported previously. Wet conditions in autumn, winter andspring in the Nordic countries aggravate the effect of heavymachinery and lead to serious subsoil quality degradation.Arvidsson et al. (2000) showed that the risk of subsoil compactionwith commonly used machinery in southern Sweden is 100% forspring slurry application and more than 60% after October in sugarbeet harvesting.
Compaction is a reduction in total porosity in a given soil mass.However, not all pores reduce proportionally. Various authors havereported a reduction due to compaction of primarily larger pores
(Bullock et al., 1985; Dorner et al., 2010; Matthews et al., 2010;Richard et al., 2001; Schaffer et al., 2007). Such pores maycompletely disappear after repeated wheeling (Pagliai et al., 2003;Servadio et al., 2005; Startsev and McNabb, 2001). This preferentialloss of larger pores can potentially change many of the mostimportant soil ecological functions, such as transmission andstorage of water, and support of plant growth and microbialactivities (Ball, 1986).
Soil compaction reduces saturated hydraulic conductivity(Horn et al., 1995) and may thus trigger surface runoff and watererosion. It may also induce preferential ow in macropores (Kulliet al., 2003; Etana et al., In review), which has been shown tofacilitate colloid transport of otherwise immobile pollutants suchas phosphorus and pesticides to receiving water bodies (Jarvis,2007). Studies of the effect of compaction on unsaturated hydraulicconductivity have produced conicting results. Richard et al.(2001) measured higher unsaturated hydraulic conductivity incompacted soil than in uncompacted. Zhang et al. (2006), on theother hand, did not observe any signicant changes in unsaturatedhydraulic conductivity. Soil compaction reduces soil aeration(Czyz, 2004) and increases emissions of the greenhouse gas N2Othrough denitrication at anaerobic sites (Bakken et al., 1987;
Received 13 October 2011
Received in revised form 14 February 2012
Accepted 16 February 2012
The ever-increasing weight of agricultural machines exacerbates the risk of subsoil compaction, a
condition believed to be persistent and difcult to alleviate by soil tillage and natural loosening
processes. However, experimental data on the persistency of subsoil compaction effects on soil pore
functioning are scarce. This study evaluated and quantied persistent effects of subsoil compaction on
soil pore structure and gas transport processes using intact cores taken at 0.3, 0.5, 0.7 and 0.9 m depth
from a loamy soil in a compaction experiment in southern Sweden (Brahmehem Farm). The treatments
included four repeated wheelings with 10 Mg wheel loads. Water retention characteristics (WRC), airpermeability (ka) and gas diffusivity (Ds/Do) were measured. A dual-porosity model tted the WRC well,
and there was a reduction in the volume of macropores >30 mm in compacted compared with controlsoil for all soil depths. Averaged for all sampling depths and also for some individual depths, both ka and
Ds/Do were signicantly reduced by compaction. Gas transport measurements showed that the
experimental soil was poorly aerated, with local anoxic conditions at water regimes around eld
capacity in all plots and depths, but with signicantly higher percentage anoxia in compacted soil. Our
main ndings were that: (1) commonly used agricultural machinery can compact the soil to 0.9 m depth,
(2) the effect may persist for at least 14 years, and (3) important soil functions are affected.
2012 Elsevier B.V. All rights reserved.
* Corresponding author. Tel.: +45 8715 4756.
E-mail address: Feto.Esimo@agrsci.dk (F.E. Berisso).
0167-1987/$ see front matter 2012 Elsevier B.V. All rights reserved.doi:10.1016/j.still.2012.02.005Persistent effects of subsoil compaction transport in a loamy soil
F.E. Berisso a,*, P. Schjnning a, T. Keller b,c, M. LamaB.V. Iversen a, J. Arvidsson b, J. Forkman d
aAarhus University, Department of Agroecology, P.O. Box 50, DK-8830 Tjele, Denmarkb Swedish University of Agricultural Sciences, Department of Soil & Environment, Box 70cAgroscope Research Station ART, Reckenholzstrasse 191, Department of Natural Resourcd Swedish University of Agricultural Sciences, Department of Crop Production Ecology, Bo
A R T I C L E I N F O A B S T R A C T
jou r nal h o mep age: w wwn pore size distribution and gas
de a, A. Etana b, L.W. de Jonge a,
, SE-75007 Uppsala, Sweden
and Agriculture, CH-8046 Zurich, Switzerland
7043, SE-75007 Uppsala, Sweden
l s evier . co m/lo c ate /s t i l l
F.E. Berisso et al. / Soil & Tillage Research 122 (2012) 4251 43Hansen et al., 1993; Simojoki et al., 1991). Poor root growth due todense and poorly aerated soil can reduce crop yield (Alakukku,1999; Hakansson and Reeder, 1994) and nutrient use efciencyand hence induce leaching of soil nitrogen.
There are only limited experimental data on the persistency ofcompaction effects on functioning of soil pores. Most existingstudies have focused on the short-term compaction effect in thetopsoil and plough-pan layers. However, detrimental structuralchanges and associated adverse effects on transport propertiesmay be especially serious in the deeper subsoil, where regenera-tion through biological activity, wettingdrying and freezethawcycles occurs at a slower rate. Compaction of deeper layers isespecially problematic since it is invisible, cumulative andpersistent (Alakukku, 2000; Hakansson and Reeder, 1994; Hornet al., 1995; Voorhees, 2000).
The objective of this study was to examine whether subsoilcompaction induced by repeated trafc with 10 Mg wheel loadshad persisted 14 years after the compaction event. A further aimwas to quantify the compaction effect on the soil pore system andits gas transport properties.
2. Materials and methods
In 2009, we revisited a eld soil compaction experimentestablished in 1995 at Brahmehem Farm (558490N, 138110E) nearKavlinge village, southern Sweden. The soil has developed onglacial till deposits and is classied as a Mollic Endogleyic Luvisolaccording to the FAO soil classication system (IUSS WorkingGroup WRB, 2006). The soil has a sandy clay loam texture, with aclay content ranging from 0.19 to 0.27 g g1. The soil organicmatter content ranges from 0.003 to 0.024 g g1. The sand contentranges from 0.45 to 0.54 g g1. We observed high texturalvariability between experimental plots at 0.7 and 0.9 m depths(data not shown).
We tted the RosinRammler (1933) distribution function toour textural data in order to characterise the mass-size distributionof the soil:
PX > x 100ex=ab (1)
where P(X > x) is the percentage of particles by weight greater thanparticle size x, e is Eulers number (base of natural logarithm), and aand b are adjustable parameters. The a parameter represents theparticle size corresponding to the 37.78th percentile of thecumulative probability distribution (Perfect et al., 1993). The greaterthe a value, the larger the soil fragment that dominates thedistribution and vice versa. The b value describes the spread ofthe particle size: the smaller the b value, the wider the spread of thefragment mass and vice versa.
For most combinations of plots and depths, the a and b valueswere in the range 73 to 128 and 0.3 to 0.48, respectively.However, there were two striking outliers, the soil samples from0.7 m depth (a = 218; b = 0.62) and 0.9 m depth (a = 330; b = 0.56)in a compacted plot, where the sand content dominated othertextural classes (data not shown). The combination of a and b forthese sampling spots indicates a relatively well-sorted, sandymaterial, and probably reects local hydraulic conditions duringthe deposition of the glacial till material.
2.2. Compaction experiment
The original eld experiment aimed to study the effect of trafcwith heavy sugar beet harvesters on soil physical properties andcrop yield (Arvidsson, 2001). The experiment had a randomisedblock design with four replicate plots. A detailed description of theexperimental set-up can be found in Arvidsson (2001). In thepresent study, plots that were not wheeled during the experimentwere used as controls, while plots subjected to four repeatedwheelings (track-by-track to cover 100% of the area in the plots)with a 35 Mg sugar beet harvester in 1995 comprised thecompacted plots.
The plots were run as a eld experiment until 1999 and thenreintegrated into the larger eld, which had been managed accordingto local farming practices in a 7-year crop rotation (winter rapewinter wheatsugar beetspring wheatwinter wheatsugar beetspring barley). The tillage regime in the eld includes mouldboardploughing (to 0.25 m depth), with occasional reduced tillage (toabout 0.1 m depth).
2.3. Vertical stress in the soil prole at the time of compaction
The sugar beet harvester used in 1995 was equipped with a0.8 m wide tyre inated to 240 kPa and the wheel load was 10.4 Mg(Arvidsson, 2001). We estimated the vertical stresses in the soilprole below