Vol. 60, 2014, No. 2: 74 79 Plnt Soil Environ. The effect of trctor wheeling on the soil properties nd root growth of smooth brome K. Krebstein 1, K. von Jnowsky 2, J. Kuht 1, E. Reintm 1 1 Institute of Agriculturl nd Environmentl Sciences, Estonin University of Life Sciences, Trtu, Estoni 2 Institute for Hygiene nd Environment, Hmburg, Germny ABSTRACT The objective of this work ws to evlute the effect of trctor wheeling with light trctor on the root growth nd soil properties of smooth brome in South Estoni. Field experiment ws conducted on sndy lom Hplic Luvisol in 2007. Dt were collected during September 2008 in both n uncompcted nd compcted re. Becuse of the compction, the precompression stress incresed in the upper soil lyer (0 10 cm) by 12.6% nd 15.2% t depth of 10 20 cm. Compction hd only minor effect on the bulk density, vlues incresed 4.7% in the upper soil lyer nd 1.8% in the deeper lyer. Differences in the sturted hydrulic conductivity (k s ) were not significnt; however, the decrese in the k s ws 26.6% in the upper level nd 12.5% in the deeper (10 20 cm) lyer. At depth of 0 to 30 cm compction decresed the root length by 44.7% nd the root mss by 60.5% compred with the uncompcted soil. Altogether, this study confirms the unfvourble effect of wheeling on grsslnds even when the wheeling is performed with light trctor on dry soil. Keywords: precompression stress; bulk density; sturted hydrulic conductivity; root length nd mss Humn ctivity, prticulrly griculturl ctivity, hs strong influence on soil properties. During the lst decdes, chnges in lnd use in Estoni hve been chrcterised by n increse in the forest re nd decrese in the re of the grsslnds (Antso nd Hermet 2012). According to the Eurostt yerbook (2011), the totl griculturl re in the 27 EU member sttes covered 172 Mh in 2007, of which 61% is rble lnd nd 33% is permnent grsslnd. The strong demnd for high qulity fodder requires more intensive use of grsslnds. However, intensive use requires high level of trffic. Over time, the power nd weight of mchines incresed (Alkukku 1999, Btey 2009). In 1970, the men wheel lods were 1 to 2 t, nd in 2000, they rnged from 2 to 3 t (Sommer et l. 2003). Schrm et l. (2012) compred different cutting regimes, trditionl versus mechnicl mowing, on grsslnds nd showed tht long-term (38 yers) mchine mowing cuses compction, prticulrly on orgnic soils. Krebstein et l. (2013) showed on sndy lom Clcric Cmbisol under lucerne tht soil compction is lso problem on frm-used grsslnds. Becuse of soil compction, the soil properties re ltered, nd reduction in soil wter nd roots cn occur (Bty 2009). The grsslnd plnt used in this study is smooth brome (Bromus inermis Leyss.). It is n invsive, cool-seson perennil Eursin grss tht is strongly rhizomtous. We used cool-seson grss in this study becuse it is more winter resistnt. Compred with cool seson grsses, wrm seson grsses hve better root growth in compcted soil (Mtthieu et l. 2011); therefore, we expected less dpttion of the smooth brome. The smooth brome cultivr in our tril ws Lehis. Supported by the Estonin Science Foundtion, Grnt No. 7622; by the Christin Albrecht University of Kiel, nd by the Germn Environmentl Foundtion. 74
Plnt Soil Environ. Vol. 60, 2014, No. 2: 74 79 There re insufficient dt on the effect of compction with light trctor on the soil properties of grsslnds. Therefore, in this study, our objective ws to investigte the effect of trctor wheeling on the soil used to cultivte smooth brome, even when soil compction does not occur under extreme conditions. Wheeling ws performed with light trctor nd smll soil contct pressure of 118 kp on dry soil (pf = 3). The hypothesis tested ws tht lthough the roots significntly contribute to soil stbility, this stbility cn be destroyed by trctor wheeling in the grsslnds. Here, the wheeling effects fter first yer of compction on the bulk density (BD), precompression stress (P c ), sturted hydrulic conductivity (k s ), root length nd root mss on the grsslnds re reported. MATERIAL AND METHODS Field site. A field experiment ws performed t the Experimentl Sttion in Rõhu, Estoni (ltitude 58 21'N, longitude 26 31'E). The reserch field ws estblished in 2007. The climte in Estoni is humid-temperte, the men nnul precipittion ws 805 mm nd the verge temperture ws 6.5 C during 2008. Soil nd smpling. The soil in the experimentl re ws Hplic Luvisol (IUSS Working Group WRB 2007). The verge soil chrcteristics were mesured prior to the beginning of the experiment in 2006. The texture of the soil ws sndy lom contining 51.5% snd (0.063 2 mm equivlent prticle dimeter), 37.4% silt (0.002 0.063 mm) nd 11.1% cly (< 0.002 mm). The verge soil chemicl chrcteristics of the experimentl field were ph KCl 5.6, C org 13 g/kg, N org 14 g/kg, vilble P 292 mg/kg, K 108 mg/kg, C 730 mg/kg nd Mg 335 mg/kg. The dt were collected from the field fter the third silge cut of smooth brome in September 2008. The sowing (38 kg/h) ws performed on 6 June 2007. The size of ech experimentl plot ws 10.5 m 2 (1.5 7 m). There were two different levels of soil compction, uncompcted nd compcted. Soil compction ws generted tyreto-tyre (tyres 8.3 20'' nd 13.6 38'') two times using trctor T-40 (2.3 Mg) with wter tnk (3 t nd tyres 7.50 20''). Trükmnn (2011) clculted soil contct pressure of 118 kp for the wter tnk ccording to O Sullivn et l. (1999). The soil wter content t depth of 0 30 cm during the soil compction in My ws pf = 2.7, nd t the end of July, the pf = 3 (these vlues do not promote the compction). The undisturbed soil smples were tken with steel cylinders for BD, precompression stress nd sturted hydrulic conductivity from depths of 10, 20 nd 30 cm nd for the root length nd mss from depths of 5, 10, 15, 20, 25 nd 30 cm on the 23 rd nd 24 th September 2008. For the BD nd k s, we used 88.2 cm 3 cylinders (dimeter 5.3 cm, height 4 cm), nd we evluted 96 smples for ech mesurement. There were 48 smples for the uncompcted re nd 48 smples for the compcted re for ech depth of 10, 20 nd 30 cm, with 16 replictions. We used 235.5 cm 3 cylinder (10-cm dimeter, 3 cm height) for the root length nd mss mesurements. For ech mesurement, there were 36 smples, of which 18 smples were from the uncompcted re nd 18 smples were from the compcted re for ech depth of 5, 10, 15, 20, 25 nd 30 cm, with three replictions. We used the sme cylinders for mesuring the P c. We evluted 16 smples, of which 9 smples were from the uncompcted res t depths of 10, 20 nd 30 cm with three replictes, nd 7 smples were from the compcted re t depth 10 cm with three replictes nd from depths of 20 cm nd 30 cm with two replictes. Lbortory methods. Soil smples were mesured in Germny t the Christin-Albrecht University of Kiel in 2009. The smples were dried in n oven t 105 C for 24 h to determine the BD. The P c ws mesured on the undisturbed soil smples, which were predrined to mtric potentil of 6 kp. A confined multi-step compression device (odometer) ws used to determine the P c. The defined pressures of 10, 20, 30, 50, 70, 100, 150, 300 nd 400 kp were pplied stepwise for 10 min to ech soil smple, nd fter 400 kp ws pplied for 10 min, no pressure ws exerted. The k s ws mesured using the flling-hed method with hood wter permemeter device. The roots were wshed out of the fresh soil on sieves with 0.25 mm mesh size. A scnner nd the WinRhizo softwre (Version 2004, Regent Instruments Inc., Quebec, Cnd) were used for the root nlysis. The wshed roots were spred out in pprox. 15 mm of wter in scnner ry (Epson 1680, Regent Instruments Inc., Quebec, Cnd). The scnner ws used for creting digitl imge of the roots tht ws then nlysed with WinRhizo. Sttisticl nlysis. For sttisticl nlysis, we used the ANCOVA to ccount for the combined 75
Vol. 60, 2014, No. 2: 74 79 Plnt Soil Environ. Tble 1. P-vlues of different fctors on investigted prmeters The compction effect ws modified by depth Soil depth Compction Interction between the soil depth nd compction Precompression stress (kp) P = 0.58 P = 0.6 P = 0.35 P = 0.36 Bulk density (g/cm 3 ) P = 0.004 P < 0.001 P = 0.005 P = 0.01 Sturted hydrulic conductivity (log, cm/dy) P = 0.3 P = 0.2 P = 0.3 P = 0.002 Root length (cm/cm 3 ) P < 0.001 P < 0.001 P < 0.001 P = 0.04 Root mss (g/m 2 ) P = 0.02 P < 0.001 P = 0.01 P = 0.06 The results were sttisticlly significnt when P < 0.05 (indicted in bold) effects of the depth nd compctions (compcted nd uncompcted). The P-vlues were evluted t 5% significnce level. The estimted vlues re reported in Tble 1. Fisher s LSD post-hoc test ws used to compre the differences between the vlues (rithmetic men). The different letters on the BD, P c nd k s grphs indicte significnt differences between the soil compction tretments t one depth. The sttisticl nlyses were performed with the R softwre version 2.15.1 (R Core tem, www.r-project.org, 2013). RESULTS AND DISCUSSION The effect of compction vried bsed on the different prmeters evluted. The soil compction hd sttisticlly significnt effect on the BD, root length nd mss. The prmeters evluted re described in Tble 1. Soil precompression stress (kp). Soil compction hd no sttisticlly significnt effect on the P c becuse of the lrge vribility in the field soil (Figure 1). However, the results showed tht compction hd negtive effect on the P c vlues. The medin P c vlues incresed in the 0 10 cm upper soil lyer by pproximtely 12.6% nd t depth of 10 20 cm by 15.2%. However, t depth of 30 cm, the result ws the opposite, the medin P c vlue in the uncompcted re ws 19% higher thn in the compcted re. Bulk density (g/cm 3 ). Soil compction nd soil depth significntly incresed the BD (Tble 1). There ws lso sttisticlly significnt difference between the uncompcted nd compcted res of the upper soil lyer (0 10 cm) (Figure 2). The difference of the medin BD vlues between the compcted nd uncompcted res ws higher in the upper lyer (0 10 cm), pprox. 4.7%, nd in the deeper lyer (10 20 cm), pprox. 1.8%. In the deepest lyer (20 30 cm), compction hd no effect on the BD. Sturted hydrulic conductivity (log, cm/dy). The chnges in k s were not obvious (Figure 3). Between the two tretments (uncompcted nd compcted), sttisticlly significnt difference Precompression stress (kp) 140 120 100 80 60 40 Uncompcted Compcted Uncompcted Compcted Uncompcted Compcted 0 10 10 20 20 30 Figure 1. Soil precompression stress (mesured t pf = 1.8) depending on soil compction nd soil depth. Error brs denote stndrd error of the men 76
Plnt Soil Environ. Vol. 60, 2014, No. 2: 74 79 Bulk Bulk density density (g/cm 3 ) 2 1.9 1.8 1.7 1.6 1.5 1.4 1.3 b Uncompcted Compcted Uncompcted Compcted Uncompcted Compcted 0 10 10 20 20 30 Figure 2. Soil bulk density depends on soil compction nd depth (uncompcted nd compcted). In the box plot, the medin ( ) nd lower upper qurtiles re shown ws observed t depths of 10 cm nd 30 cm. In the upper lyer (0 10 cm), the medin k s vlue ws pprox. 26.6% higher between the trffic lnes compred with no trffic lne, nd in the deeper lyer (10 20 cm), the medin k s vlue incresed by 12.5%. Becuse of compction, the P c vlues in the upper soil lyer (0 20 cm) incresed compred with the uncompcted re. Krebstein et l. (2013) found tht due to soil compction, the P c incresed in the upper soil lyer to 60 kp nd to 30 kp t soil depth of 10 cm. According to our results, we cn ssume tht the binding substnces re not relly chnged, hence, the number of contct points must be incresed (verified by BD). During soil deformtion, the soil prticles re pushed more closely towrds ech other, which leds to higher BD with greter number of contct points between the soil prticles (Lebert nd Horn 1991). Wheeling with light trctor incresed the BD; however, the increse ws smll nd better observed in the upper soil lyer (0 10 cm). Bsed on our results, wheeling does not chnge the BD vlues in the deeper soil lyer (20 30 cm). This is becuse soil compction chnges the soil structure, but this does not chnge the BD results s the BD does not reflect the soil structure. O Sullivn et l. (1999b) demonstrted the influence of decresed pore continuity by shering on the ir conductivity t the sme BD. When the bulk soil is compcted, the k s vlues re lowered. This is lso consistent with the literture. Zhng et l. (2006) showed tht soil compction ffected the hydrulic properties on loess soils. Sturted hydruclic conductivity (log) 3.5 3 2.5 2 1.5 1 0.5 0 b b Uncompcted Compcted Uncompcted Compcted Uncompcted Compcted 0 10 10 20 20 30 Figure 3. Sturted hydrulic conductivity depends on soil compction nd soil depth. In the box plot, the medin ( ) nd lower upper qurtiles re shown 77
Vol. 60, 2014, No. 2: 74 79 Plnt Soil Environ. They showed tht the k s vlues decresed when the soil compction incresed. However, the increse in k s vlues below 10 cm in our study my hve occurred becuse the roots my block the pores (more roots in uncompcted soil), thereby reducing the k s vlues, lthough they my hve more lrge pores. Root length (cm/cm 3 ) nd root mss (g/m 2 ). Our results showed tht fter first yer of compction, the root length nd mss chnged becuse of compction. The longest roots were in the upper soil lyer (Figure 4). The verge root length in uncompcted re t ll depths incresed pprox. 44.7% compred with the compcted re. In the upper uncompcted lyer (0 15 cm), the roots were 47.6% longer thn in the compcted re, nd in the deeper soil lyer (20 30 cm), the difference ws 36.6%. The root mss in the compcted soil ws less thn in the uncompcted soil (Figure 4b). The verge root mss in the compcted re t ll depths ws 60.5% less thn the uncompcted re. The root mss of the smooth brome ws greter in the upper soil lyer (0 15 cm) compred with the deeper soil lyer (20 30 cm), nd for the compcted nd the uncompcted res, the difference in the root mss of the upper lyer ws 64.4%. In the deeper lyer, the soil compction decresed the root mss by 29.6%. The ltertions in the root length nd mss re more pronounced in the upper soil lyer (0 15 cm). This is becuse the light trctor hd more influence on the soil surfce thn the subsoil. Tolón-Becerr et l. (2012) showed tht the subsoil compction is relted to the trctor weight, with lightweight trctors exerting less pressure on the soil contct re. According to Lipiec et l. (2003), the root size of ots ws more ffected in the ploughed lyer compred with the deeper soil. Becuse of compction, the roots cnnot penetrte the deeper lyers nd therefore sty t the top. This is lso confirmed by literture. Lipiec et l. (1991, 2003) showed tht soil compction led to higher concentrtion of roots in the upper lyer nd reduced the roots in the deeper lyer. In greenhouse study, Mtthieu et l. (2011) found tht subsurfce compction impeded turf grss root growth in the deep lyers. In five-yer tril on non-grzed temporry grsslnd (lomy snd) with different lods (0, 4.5, 8.5 nd 14.5 t), Bouwmn nd Arts (2000) showed tht when wheeling ws performed with mximum lod (14.5 t), the mjority of the root mss ws bove 20 cm. Głąb (2008) showed tht wheeling ffected the root length on silty lom Mollic Fluvisols, nd the root length ws shorter in ll soil lyers (0 30 cm) fter wheeling. Altogether, this study confirmed the unfvourble effect of trctor trffic even when soil compction does not occur under extreme conditions on the grsslnd, such tht the soil is dry nd the trctor contct pressure is low. Our experiment shows tht the precompression stress, soil bulk density, sturted hydrulic conductivity, root length nd mss is significntly ffected by wheeling. In response to the trctor trffic, the soil stbility prmeters, such s P c incresed. After the first yer of compction event, the effect of compction () 5 (b) 5 10 10 15 20 15 20 25 30 Uncompcted Compcted 0 10 20 30 Root length (cm/cm 3 ) 25 30 0 50 100 150 200 Root mss (g/m 2 ) Figure 4. The verge root length () in the soil nd the verge root mss (b) in the soil depend on the soil compction (uncompcted nd compcted) nd depth. The horizontl brs denote the stndrd errors 78
Plnt Soil Environ. Vol. 60, 2014, No. 2: 74 79 ws visible becuse the soil physicl properties, such s BD, were incresed on the compcted soil. As result, the root systems djusted to the new stte nd formed less roots in totl, prticulrly in the topsoil. Soil compction lso decresed the k s vlues in the upper soil lyer, when the bulk soil is compcted, it lowers the k s vlues. In conclusion, our results confirmed the negtive effect of wheeling even when the wheeling does not occur under extreme conditions, on the root growth nd soil properties of smooth brome. REFERENCES Alkukku L. (1999): Subsoil compction due to wheel trffic. Agriculturl nd Food Science in Finlnd, 8: 333 351. Antso K., Hermet I. (2012): Estonin Environmentl Indictors. Avilble t http://www.envir.ee/orb.w/clss=file/ ction=preview/ id=1190570/eesti±keskkonnn%e4itjd±2012. pdf [ccessed 16.07.2013] (In Estonin) Btey T. (2009): Soil compction nd soil mngement review. Soil Use nd Mngement, 25: 335 345. Bouwmn L.A., Arts W.B.M. (2000): Effects of soil compction on the reltionships between nemtodes, grss production nd soil physicl properties. Applied Soil Ecology, 14: 213 222. Eurostt yerbook (2011): Avilble t http://epp.eurostt. ec.europ.eu/portl/pge/portl/publictions/eurostt_yerbook_2011 [ccessed 20.03.2012] Głąb T. (2008): Effects of trctor wheeling on root morphology nd yield of lucerne (Medicgo stiv L.). Grss nd Forge Science, 63: 398 406. IUSS Working Group WRB. World Reference Bse for Soil Resources 2006, first updte 2007. World Soil Resources Reports No. 103, FAO, Rome. Krebstein K., von Jnowsky K., Reintm E., Horn R., Leeduks J., Kuht J. (2013): Soil compction in Cmbisol under grsslnd in Estoni. Zemdirbyste-Agriculture, 100: 33 38. Lebert M., Horn R. (1991): A method to predict the mechnicl strength of griculturl soils. Soil nd Tillge Reserch, 19: 275 286. Lipiec J., Hknsson I., Trkiewicz S., Kossowski J. (1991): Soil physicl properties nd growth of spring brley relted to the degree of compctness of two soils. Soil nd Tillge Reserch, 19: 307 317. Lipiec J., Medvedev V.V., Birks M., Dumitru E., Lyndin T.E., Roussev S., Fuljtr E. (2003): Effect of soil compction on root growth nd crop yield in Centrl nd Estern Europe. Interntionl Agrophysics, 17: 61 69. Mtthieu D.E., Bowmn D.C., Thp B.B., Cssel D.K., Rufty T.W. (2011): Turfgrss root response to subsurfce soil compction. Communictions in Soil Science nd Plnt Anlysis, 42: 2813 2823. O Sullivn M.F., Henshll J.K., Dickson J.W. (1999): A simplified method for estimting soil compction. Soil nd Tillge Reserch, 49: 325 335. O Sullivn M.F., Robertson E.A.G., Henshll J.K. (1999b): Sher effects on gs trnsport in soil. Soil nd Tillge Reserch, 50: 73 83. R Core Tem (2013): R: A Lnguge nd Environment for Sttisticl Computing. R Foundtion for Sttisticl Computing, Vienn. Avilble t http://www.r-project.org Schrm M.J.J., Cordlndwehr V., Visser E.J.W., Elzeng T.M., de Vries Y., Bkker J.P. (2012): Grsslnd cutting regimes ffect soil properties, nd consequently vegettion composition nd belowground plnt trits. Plnt nd Soil, 336: 401 413. Sommer C., Lebert M., Brunotte J. (2003): Indiktoren zum physiklischen Bodenschutz wrum, wofür, wie? In: Dchverbnd Agrrforschung: Umweltindiktoren Schlüssel für eine umweltverträgliche Lnd- und Forstwirtschft. DAF-Schriftenreihe grrspectrum, 36: 175 186. (In Germn) Tolón-Becerr A., Bott G.F., Lstr-Brvo X., Tourn M., Rivero D. (2012): Subsoil compction from trctor trffic in n olive (Ole europe L.) grove in Almerí, Spin. Soil Use nd Mngement, 28: 606 613. Trükmnn K. (2011): Quntifizierung der Stbilisierungseffekte von Pflnzenwurzeln ls Möglichkeit zur Reduzierung der mechnischen Bodendeformtionen in Grünlnd. [PhD. thesis] Avilble t CAU. http://eldiss.uni-kiel.de/mcu/receive/disserttion_diss_00006942 [ccessed 15 03 2012] (In Germn) Zhng S., Grip H., Lövdhl L. (2006): Effect of soil compction on hydrulic properties of two loess soils in Chin. Soil nd Tillge Reserch, 90: 117 125. Received on November 12, 2013 Accepted on Jnury 17, 2014 Corresponding uthor: MSc. Kdri Krebstein, Estonin University of Life Sciences, Deprtment of Soil Science nd Agrochemistry, Institute of Agriculturl nd Environmentl Sciences, Kreutzwldi 1, 51014 Trtu, Estoni e-mil: Kdri.Krebstein@emu.ee 79