Effect of soil compaction and N fertilization on soil pore characteristics and physical quality of sandy loam soil under red clover/grass sward
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Soil & Tillage Research 144 (2014) 819Effect of soil compaction and N fertilization on soil pore characteristicsand physical quality of sandy loam soil under red clover/grass sward
Tomasz Gab *Institute of Machinery Exploitation, Ergonomics and Production Processes, University of Agriculture in Krakow, ul. Balicka 116B, Krakow 31-149, Poland
A R T I C L E I N F O
Article history:Received 2 September 2013Received in revised form 28 April 2014Accepted 17 May 2014
Keywords:Nitrogen fertilizationSoil compactionRed cloverGrassesSoil porositySoil water retention
A B S T R A C T
During the 20th century grassland production systems were intensified with higher rates of nitrogenusage and increasing heavy vehicular activity. This tendency is reflected in the higher soil degradationrisk. However, in recent years European agri-environmental policies have promoted low-input grasslandmanagement practices. These changes in fertilization intensity may interact with the effects of machinetraffic in affecting soil physical properties. The objective of this study, was to investigate the influence ofsoil compaction caused by tractor traffic and N fertilization levels on a soil pore system under a clover/grass mixture during the period from 2010 to 2012. This experiment was established in a split-plot designwith fertilization as a main plot and soil compaction as a subplot. The N fertilizer treatments used were:untreated control (N0), 80 kg N ha1 (N80) and 160 kg N ha1 (N160). Four compaction treatments wereapplied using the following number of tractor passes: untreated control (P0), two passes (P2), four passes(P4) and six passes (P6). Undisturbed soil samples were collected in 20102012 in order to determine thewater retention parameters and morphometric characterization of soil pores. The soil watercharacteristic curve was determined using pressure plates. The soil macropore system was alsocharacterized using image analysis on the sections of soil samples hardened with polyester resin.The mineral fertilization did not significantly affect any physical parameters of soil at the trial. Theintensive wheeling resulted in a higher value of bulk density and penetration resistance and lower valuesof total porosity. The soil compaction has distinctly influenced the soil water retention characteristics inthe high matric potential range, which corresponds mainly with large pores (transmission pores andfissures) and storage pores. The result of changes in soil porosity was to increase the plant available watercapacity. On the other hand, the relative field capacity indicated that in compacted soil under grasslandplants, the biological activity was limited by insufficient soil aeration. This conclusion is in agreementwith the results in plant production, which showed decrease in root and above ground biomass as theresult of compaction.
2014 Elsevier B.V. All rights reserved.
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Soil & Tillage Research
journal homepage: www.else vie r .com/locate /s t i l l1. Introduction
Agricultural production systems tend to increase the number ofpasses and the loads carried on agricultural vehicles, resulting in apotential for increased soil compaction (Newell-Price et al., 2013).According to the EU Commission, soil compaction is recognized asone of the main factors that can lower crop yields and thus hasbecome a serious agricultural problem (European Commission(EC), 2006). Compaction leads to soil structure degradation, whichresults in a deterioration in physical properties. Associated withthis bulk density and soil strength, measured as penetrationresistance, are increased (Richard et al., 2001; Pagliai et al., 2003;* Tel.: +48 12 662 45 51.E-mail address: firstname.lastname@example.org (T. Gab).
http://dx.doi.org/10.1016/j.still.2014.05.0100167-1987/ 2014 Elsevier B.V. All rights reserved.Hamza and Anderson, 2005). To quantify soil structural changesfollowing agricultural activities, besides traditional measurementssuch as bulk density, penetration resistance, total porosity, andpore space measurements are being increasingly used (Pagliaiet al., 2004). The soil pore system is widely recognized as beingresponsible for available soil water content and aeration porosity,which affect root and crop growth. Changes in soil porosity arereflected in the water retention characteristics and are extremelyimportant in irrigation systems (Nawaz et al., 2013).
The effect of soil compaction depends on the compaction effort,soil type, water status, landscape position, and cropping systeminvolved (Green et al., 2003; Sillon et al., 2003; Tarawally et al., 2004;Zhang et al., 2006). It is a serious problem for perennial crops, wherethesoil issubjectedtotraffickingwithoutanannual tillageoperation.Soil strength increased year-after-year due to machine traffic duringfield operations. The wheels of these machines cause direct plant
Table 2Average monthly temperature and total precipitation at the experimental siteduring the period 20102012 plus the long-term averages.
2010 2011 2012 19611990
Monthly average temperature (C)January 6.3 1.2 1.2 1.9February 2.2 2.6 6.6 0.8March 3.3 3.6 4.4 4.4April 9.0 10.3 9 4 7.2May 12.8 13.5 15.0 13.6June 17.5 18.2 17.4 15.1July 20.7 17.7 20.3 17.1August 18.4 19.0 18.9 16.6September 12.3 14.1 14.0 10.5October 8.7 8.6 8.6 5.9November 3.1 2.1 5.0 0.5December 2.3 1.6 2.9 2.4Annual mean 7.9 8.7 8.5 7.4
Sum of monthly precipitation (mm)January 44 26 52 34February 32 8 28 32March 31 15 17 34April 40 78 49 48May 299 48 18 83June 135 33 144 97July 105 186 71 85August 128 73 55 87September 113 14 44 54October 14 32 96 46November 27 0 22 45December 43 38 27 41
Annual sum 1010 552 622 681
Table 1Basic soil physical and chemical properties of Mollic Fluvisol from the trial location(020 cm layer).
pH(KCl) 6.5Organic C g kg1 12.5Total N g kg1 1.39C:N ratio 9.0P mg kg1 107.2K mg kg1 138.0Mg mg kg1 67.9Solid particle density Mg m3 2.65Sand g kg1 560Silt g kg1 270Clay g kg1 170Texture Sandy loam
T. Gab / Soil & Tillage Research 144 (2014) 819 9damage, which are reported to be as important in terms ofcontributing to decreased plant yield as soil compaction. Moreover,perennial forage crop production demands a very intense vehicularactivity, especially during crop harvesting operations (Jorajuria andDraghi,1997). Inrecentyearsmorepowerful and heaviertractors andmachinery have been used on farms.
On the other hand the extensification in livestock productionthat is promoted by the EU results in a reduction in stocking rateand fertilizer application (European Union, 1998). The design andimplementation of the resulting national agri-environmentalschemes radically modified the direction of grassland systemdevelopment in the EU. One of the most important changes was inthe regulation and incentives designed to limit grassland fertilizerapplication in order to reduce nutrient losses and mitigate soil andwater pollution (Gibon, 2005).
The soil physical properties can be modified by mineralfertilization in two ways. The most direct impact is achieved bymodifying the chemical composition of the soil solution, its ionicstrength, pH and soil aggregate stability (Schroder et al., 2011;Bronick and Lal, 2005). The major benefits of fertilizers on soilproperties are improved crop yields, by increasing the root andresidue biomass in soil, thereby resulting in higher organic mattercontent. Organic matter has been shown to have beneficial effects onsoil structure and leads to higher hydraulic conductivity (Gab andKulig, 2008; Hargreaves et al., 2008). The increase in soil organiccarbon reduces bulk density and increases water holding capacityand soil aggregate stability (Celik et al., 2004; Herencia et al., 2011).Researchers have also reported an increase in the field capacity andwilting point (Chang et al., 1983). These changes in the physicalproperties are ascribed to the mixing of soil with less dense organicmaterial (Khaleel et al., 1981). These effects are most clearlyidentified in relatively compacted, fine-textured soils (Aggelidesand Londra, 2000; Celik et al., 2004) or in coarse-textured soils(Turner et al., 1994). Many parameters affect the physical propertiesof soil, so that a specific impact derived from NPK treatment issometimes hard to demonstrate. It is usually low, especially whencompared to the impact of crop residues or management practices(Simansky et al., 2008). Most of the available information in theliterature deals with annual crops. However, the interaction betweenthe effect of soil compaction and the effect of fertilization used ongrasslands has not, so far, been studied.
In this study, we assessed the effect of different N fertilizationrates and trafficking intensity on the soil quality. The objective of thestudy was to evaluate the water retention characteristics and themorphometric characterization of soil pores with a wide diameterrange running from 0.005 to >2000 mm with a special focus onmacropores investigated using image analysis of soil sections.
2. Material and methods
2.1. Site, location and climate
This study was conducted as a field experiment located inMydlniki near Krakow, Poland (50040N,19510E, 211 m a.s.l.) over athree-year period (20102012). The field experiment was locatedon sandy loam Mollic Fluvisol (IUSS Working Group WRB, 2007).Table 1 details some of the soil characteristics. The climate of theexperiment site is temperate-continental. Average annual precipi-tation reaches 681 mm per year, and the mean daily temperature isarou