Vol. 17 (2008): 153 164. Effect of Cirsium rvense L. on soil physicl properties nd crop growth Endl Reintm, Ktrin Trükmnn, Jn Kuht, Avo Toomsoo, Triin Teeslu, Tiin Köster Estonin University of Life Sciences, Institute of Agriculturl nd Environmentl Sciences, Kreutzwldi 1, 51014 Trtu, Estoni, emil: endl.reintm@emu.ee Liin Edesi, Edvin Nugis Estonin Reserch Institute of Agriculture, Teduse 13, 75501 Sku, Estoni The re-cultivtion of bndoned res cretes weed control problems. The min problems in these res re perennil weeds, such s Cirsium rvense L. but this perennil deep-rooted plnt my hve beneficil effect on the physicl properties of compcted soil. In order to study the effect of C. rvense s root system on soil properties, the field experiment nd survey of rble fields were conducted in Estoni. The soil bulk density nd penetrtion resistnce were mesured from soils covered by C. rvense or spring brley (Hordeum vulgre L.) on compcted nd un-compcted soil. The results showed significntly lower penetrtion resistnce nd bulk density underneth C. rvense thn under brley in both the field experiment nd field survey on rble soils. The shoot mss of C. rvense ws less ffected thn the shoot mss of brley by soil compction nd ws cused by C. rvense s better bility to develop its root system in compcted soil. Whet yield, on soils ffected by C. rvense, ws incresed by 28% on loose soil nd 37% on compcted soil. It my be concluded tht in res ffected by deep-rooted weed species, such C. rvense, the soil s physicl properties will improve t lest in the first two yers. Key-words: soil, Cirsium rvense, brley, whet, penetrtion resistnce, bulk density, roots Introduction Agriculture is thret to soil qulity due to hevy use of the lnd for securing food for people nd nimls. The min threts to soil qulity in Europen context re erosion, decline in orgnic mtter, soil contmintion, soil seling, soil compction, decline in soil biodiversity, sliniztion, floods nd lndslides. One third of the rble lnd in Estoni is ffected by some kind of degrdtion (FAO 2000) nd bout 11% by soil compction Agriculturl nd Food Science Mnuscript received December 2006 153
Reintm, E. et l. Cirsium rvense on rble soils (vn Lynden 2000). The re of Estonin rble lnd hs decresed, since the re-estblishment of the independence of Estoni in 1991, to 53% of the previous level (Astover et l. 2006). The re-cultivtion of bndoned res cretes weed control problems. Four to six yers fter the termintion of cultivtion Elytrigi repens L., Cirsium rvense L. nd other perennil species become predominnt in the fields. The presence of lrge number of rhizomes nd roots nd high weed seed density in the soil (Luringson nd Tlgre 2003), cretes need for higher mechnicl control of weeds in the initil re-cultivtion yers, especilly if the lnd ws not cultivted for long time. C. rvense is persistent weed tht cuses problems in crop fields, grsslnds nd pstures s well s on fllow nd nture conservtion res in temperte regions of both hemispheres (Donld 1994). C. rvense grows on vriety of soil types. It does well on deep, well erted, moist lom soils, but is known to grow in dry hbitts nd on sndy soils. It my lso grow on strem bnks, in medows, nd even in wet ditches, but it will not survive in sturted soil. It is intolernt of shde, requiring good light conditions for ggressive growth (Moore 1975). C. rvense hs now become one of the severest perennil weed problems in orgnic griculture in north Europen countries, prticulrly in crop rottions with high proportion of cerels (Slonen et l. 2001, Grgli et l. 2006). However, C. rvense hs n extensive root system, which is ble to grow s deep s 6.8 m, but commonly the roots rech depth of 1.5 m in oneyer old plnts, nd 2 m in two to ten yer old plnts (Ndeu 1989). The root weight of C. rvense verges 1100 g m -2 nd decreses with depth, from 500 g m -2 in the top 30 cm, to 350 g m -2 in 31 60 cm, nd 250 g m -2 in 61 90 cm depth (Donld 1994). It hs been estblished tht more thn 20 culturl plnts species re ble to sufficiently develop their root system in dense nd strong soil (Mtercher et l. 1991). Tht kind of penetrtion of plnt roots into compcted soil hs been described s possible nturl process, which my meliorte compcted soil (Willims nd Weil 2004). Plnts modify soil structure minly when their roots grow into the dense lyers, then lter die nd decy leving behind pores or chnnels tht re termed biopores (Yunus nd Newton 2003). The hypothesis of the current study ws tht C. rvense due to its vigorous root system my lso be ble to penetrte compcted soil nd loosen it in which cse there would be substntil benefit from hving C. rvense on fllow lnd. In order to study the hypothesis the field survey on rble fields with high level of C. rvense infesttion ws conducted to determine if C. rvense hd chnged the soil penetrtion resistnce of fields ffected by it. In order to study the effect of C. rvense in more controlled conditions nd to find out the residul effect of C. rvense, the field experiment ws estblished. The ims of the field experiment were complex investigtions of the soil nd C. rvense. The min gols of the current study were to investigte: 1) chnges in soil penetrtion resistnce nd bulk density due to compction nd C. rvense; 2) the mss nd density of root nd shoots of C. rvense due to compction nd 3) the residul effect of C. rvense growing on compcted soil on the development nd yield of spring whet (Triticum estivum L.). Spring brley (Hordeum vulgre L.) growing on compcted nd un-compcted soils were used s control tretments. Mteril nd methods Dt from field survey were collected from the fields of five Estonin counties in the yer 1997. Dt from field experiment were collected from the reserch field of the Estonin University of Life Sciences on sndy lom surfce Stgnic Luvisol t Trtu County in Eerik (58º23 N, 26º44 E) in the yers 2004 2006. Survey on the rble fields In order to study the effect of C. rvense growing on soil properties on rble fields, survey ws 154
Vol. 17 (2008): 153 164. conducted t six loctions in five counties in Estoni. The loctions under survey were Rõngu nd Eerik in Trtu, Helme in Vlg, Näsre in Viljndi, Kergu in Pärnu nd Loorits in Järv. Those fields in which C. rvense ws present nd hd been bndoned for four yers were selected to mesure soil penetrtion resistnce inside C. rvense colonies nd in soil where C. rvense ws not growing. The crops growing in the fields were ot (Aven stiv L.) in Rõngu, Helme nd Kergu, spring whet in Näsre nd spring brley in Loorits nd Eerik. The soil types of the six investigted loctions during the field survey were the following in WRB 1998 clssifiction (FAO 1998): Eerik sndy lom Stgnic Luvisol, Rõngu lomy Gleyi-Dystric Luvisol, Helme lomy snd Dystric Luvisol, Näsre sndy lom Stgnic Luvisol, Kergu silty lom Clcric Regosol nd Loorits sndy Hplic Luvisol. During the soil survey the soil penetrtion resistnce, soil moisture content nd shoot density nd mss of C. rvense were investigted. No detiled investigtions on soil density nd other prmeters were mde s the gol of the study ws to detect if there re some differences t ll between res with nd without C. rvense in soil physicl prmeters. Penetrtion resistnce for the field survey ws mesured to depth of 40 cm. From the sme depths were tken smples to mesure soil moisture content. Field experiments The field experiment ws estblished in 2001. A 4.9 tonne, MTZ-82 trctor ws used to compct the soil before sowing time in spring 2001, 2002, 2003, 2004 nd 2005. Six repeted psses with wheeled triler loded with 2.22 tonne on the front xle nd 2.62 tonne on the rer xle (totl lod ws 4.84 tonne) uniformly covered the entire experimentl plot re. The infltion pressure in the wheels of the trctor ws 150 kp. Two compction tretments were estblished on the experimentl field. The re without specil compction served s the control. The compction tretments were split into four replictions (16 plots) nd the size of ech experimentl plot ws 12 9 m (108 m 2 ). Drilling of brley (crosswise to compction tretments) t rte of 450 germinting seeds per m 2 ws conducted in the middle of My. No fertilizers nd herbicides were used in the experiment. Ech compction tretment plot ws split into deep-rooted species tretments (size of ech plot 3 9 m) in 2004. C. rvense ws plnted with density of 16 plnts per m 2 in spring of 2004 to 15 cm depth. Plnted plnts were pproximtely 10 cm high with t lest 5 cm horizontl root frgment. Brley tretment served s control. Both tretments were compcted gin in spring of 2005. Specil compction ws not mde in 2006 nd the whet ws sown (t the rte of 500 germinting seeds per m 2 ) over the entire experiment re to estblish the residul effect of C. rvense nd brley. Every utumn (in September) the soil ws ploughed to depth of 21 22 cm. The surfce soil type of the experiment re ws sndy lom Stgnic Luvisol in the WRB 1998 (FAO 1998) clssifiction. Anlysis of the genetic nd dignostic horizons indicted tht the horizons of humus (32 cm), ferrlic ccumultion (8 cm), stgnic (10 cm) nd rgillic (29 cm) were found in the soil profile. The soil chrcteristics (t the beginning of experiment in 2001) of the humus horizon (30 cm) were: C org 1.4%, N tot 0.11%, vilble K 164 mg kg 1, P 183 mg kg 1, C 674 mg kg 1, Mg 101 mg kg 1, ph KCl 6.2, snd (2.0 0.02 mm) 67.9%, silt (0.02 0.002 mm) 22.9% nd cly (<0.002 mm) 9.2%. The brupt texturl chnge strted t 50 cm depth with 49% snd, 30% silt nd 20% of cly. The investigted soil formed on bisequl-textured reddish-brown till nd is sensitive to soil compction. This type of soil covers 5.9% of the totl re, nd 15.1% of the rble lnd in Estoni, mostly in the south nd the south-est (Reintm nd Köster 2006). Field smpling The smples of soil nd plnts were tken in the ering phse of brley in growth stge 75 79 by the numeric code description ccording to the BBCH 155
Reintm, E. et l. Cirsium rvense on rble soils (Biologische Bundesnstlt, Bundessortenmt nd CHemicl industry) Growth Scle of plnts (Lncshire et l. 1991). Dt regrding the botnicl composition of the plnt community were obtined from tking vegettion smples from plot of 0.25 m 2 (n = 4). The types of plnt community components (brley nd different weed species) were determined, counted, mesured nd weighed. Root smples were tken using 1131 cm 3 (h = 15 cm, Ø = 9.8 cm) steel cylinders in 15 cm lyers down to 60 cm in 4 replictions. The soil from the cylinders ws weighed nd the soil bulk density clculted before root wshing on 0.5 mm sieve. Penetrtion resistnce ws mesured with hnd cone penetrometer (cone ngle 60º, stick dimeter 12 mm) in every 5 cm lyer down to 60 cm in six Tble 1. Soil moisture content (g kg -1 ) during field survey underneth of Cirsium rvense L. nd spring brley (Hordeum vulgre L.) in 0 40 cm depth in the ering phse of brley (in middle of July). In prentheses is the stndrd error of the men. Loction Cirsium rvense L. Hordeum vulgre L. Rõngu 197(11) 192(18) Helme 161(8) 160(10) Näsre 196(5) 193(7) Kergu 182(3) 174(10) Loorits 163(12) 189(4) Eerik 211(17) 204(13) replictions from every experimentl plot. Smples for mesuring soil moisture content were tken from the sme lyers. Soil moisture ws mesured both in the spring, fter specil compction, nd in summer t the sme time s the soil penetrtion resistnce mesures. To find out the wter content in the soil, the soil smples tken from the field (by 50 cm 3 cylinders) were weighted nd dried t 105 C to the constnt weight nd weighted gin. After tht the wter content ws clculted s follow: Ww - Dw moisture, % = # 100, Dw where Ww is soil wet weight nd Dw is soil dry weight in grms. Soil moisture content t compction ws 170 180 g kg -1 (-60 to -70 kp) in 2004 nd 2005. Soil moisture content in the ering phse of brley is presented in Tbles 1 nd 2. Wether conditions In yer 1997 more precipittions occurred in My nd June nd less in July nd August (Tble 3). The end of August ws wrmer s in most yers. During the field experiment the riniest yer ws 2004, when it ws 475 mm precipittions during growing period (Tble 3). In 2005 nd 2006 only 282 nd 161 mm of rin ws recorded, respectively. More precipittion Tble 2. Soil moisture content (g kg -1 ) during field experiment underneth (2004 2005) nd ginst the bckground (2006) of Cirsium rvense L. nd spring brley (Hordeum vulgre L.) in the ering phse of brley (in middle of July). In prentheses is the stndrd error of the men. Yer Soil depth (cm) Cirsium rvense L. Hordeum vulgre L. 2004 0 30 218(10) 204(4) 200(7) 189(12) 30 60 160(2) 166(9) 151(8) 148(11) 2005 0 30 91(4) 82(7) 150(12) 142(5) 30 60 87(6) 81(6) 108(3) 113(8) 2006 0 30 135(2) 121(11) 153(3) 151(7) 30 60 93(5) 91(6) 99(9) 91(5) 156
Vol. 17 (2008): 153 164. occurred in June nd August, less in July. Averge ir temperture ws highest in August (17.1 C) in 2004 nd in July in 2005 nd 2006. Sttistics The three-wy nlysis of vrince (ANOVA) ws used to determine the impct of the tril fctors bsed on the collected dt. The fctors were soil depth, compction nd plnt species. The Fisher test ws used to compre the differences between vlues nd lest significnt differences (LSD) t significnce p < 0.05 detected nd the significnce between tretments estimted. The stndrd error of the men ws, for the presenttion of the dt in the figures, clculted. The progrm Sttistic 7.0 ws used for dt nlysis (SttSoft 2006). Results Field survey The field survey on Estonin rble lnd ffected by C. rvense, which hve been bndoned for four yers nd thn re-cultivted, reveled the loosening effect of C. rvense roots on compcted soil. Soil penetrtion resistnce underneth C. rvense ws lower in ll investigted loctions thn under crops (Fig. 1). A significntly lower soil penetrtion resistnce under C. rvense ws found in Rõngu, Näsre nd Kergu. However, no significntly higher moisture content ws detected under C. rvense (Tble 1). The verges for the mss of C. rvense shoots were 580 g m -2, with density of shoots t 33 m -2 nd height 1.2 m (Tble 4). There ws bout 7 8 C. rvense ptches per hectre, except Tble 3. Wether conditions of experiment yers (1997, 2004 2006) during spring brley (Hordeum vulgre L.) growing period. Months nd Precipittions (mm) Men ir temperture ( C) decdes * 1997 2004 2005 2006 1997 2004 2005 2006 My I 33.6 10.2 14.8 0.0 7.0 15.6 7.6 14.1 II 5.1 4.0 52.8 16.4 11.8 7.2 9.8 10.8 III 26.1 20.0 46.4 15.2 8.6 13.6 14.9 10.9 June I 3.5 46.6 17.8 36.8 15.7 13.4 12.4 11.5 II 81.6 20.6 18.4 0.2 16.2 12.3 15.6 18.6 III 30.5 143.4 18.0 10.0 16.7 14.5 15.3 18.7 July I 22.9 28.0 0.0 10.0 20.0 15.1 19.1 21.0 II 2.6 20.0 3.0 0.0 16.1 15.8 21.2 18.2 III 9.3 65.6 18.6 6.2 19.6 18.3 17.6 17.2 August I 11.4 3.2 75.8 13.6 20.6 20.0 17.4 17.0 II 19.3 53.0 7.0 16.2 14.6 15.9 16.2 17.9 III 0.0 34.4 9.6 36.4 21.2 13.7 16.1 16.2 * Decde ten dy period of month 157
Reintm, E. et l. Cirsium rvense on rble soils Penetrtion resistnce (MP ) 7 6 Crop Cirsium rvense L. Fig. 1. Soil penetrtion resistnce depending on Cirsium rvense L. growing on six rble fields in Estoni: Rõngu lomy Gleyi-Dystric Luvisol, Helme lomy snd Dystric Luvisol, Näsre sndy lom Stgnic Luvisol, Kergu silty lom Clcric Regosol nd Loorits sndy Hplic Luvisol, Eerik sndy lom Stgnic Luvisol. An verge of top 40 cm soil lyer. Box: men ± stndrd error. Whisker: men ± 0.95 confidence intervl. 5 4 3 2 1 0 Rõng u Helme Näsre Kergu Loorits Eerik Loction Tble 4. Cirsium rvense L. shoots density (plnts m -2 ) nd dry weight (g m -2 ) in ptch on six rble field of Estoni: Rõngu lomy Gleyi-Dystric Luvisol, Helme lomy snd Dystric Luvisol, Näsre sndy lom Stgnic Luvisol, Kergu silty lom Clcric Regosol nd Loorits sndy Hplic Luvisol, Eerik sndy lom Stgnic Luvisol. In prentheses is the stndrd error of the men. Loction Density (plnts m -2 ) Shoot weight (g m -2 ) Rõngu 35(12) 670(108) Helme 27(6) 464(67) Näsre 43(19) 632(105) Kergu 21(9) 568(130) Loorits 44(12) 617(187) Eerik 29(7) 534(101) in Helme, where the field ws totlly covered with ptches nd only some 30 56 m 2 res were without C. rvense. The next most widespred weed species fter C. rvense were Sonchus rvensis L., Elytrigi repens L., Artemisi vulgris L. nd lso Tussilgo frfr L. Field experiment Direct effect The results of the field experiment reveled soil compction hd hrmful effect on spring brley nd C. rvense bove ground mss in the first yer, 2004 (Fig. 2). C. rvense incresed its shoot mss in the second yer, 2005, nd the mss ws twice s much on compcted thn on un-compcted soil. Compction, however, hd only negtive effect on brley shoots decresing their mss by 50% in the reltively dry yer of 2005. The shoot density of C. rvense ws greter by 30 plnts per m 2 on un-compcted soil in the first yer thn on compcted soil (Fig. 3). The results the next yer were the exct opposite, 30 plnts per m 2 more on compcted soil. Shoot density of spring brley ws 1.6 times higher in yer 2004, thn in yer 2005 (Fig. 3b). Brley shoot density, however, did not decrese significntly in yer 2005 s result of compction. The root mss of brley decresed rpidly s soil bulk density nd depth incresed (Fig. 4b). The roots in compcted soil concentrted more in the soil surfce horizon (15 cm) while lmost no roots 158
Vol. 17 (2008): 153 164. Shoots weight (g m -2 ) 700 600 500 200 100 Cirsium rvense L. c bc Yer 2004 Yer 2005 d () 700 600 500 200 100 Hordeum vulgre L. c b bc Yer 2004 Yer 2005 (b) Fig. 2. The shoots dry weight (g m -2 ) of Cirsium rvense L. () nd spring brley (Hordeum vulgre L.) (b) depending on soil compction. Brs denote the stndrd error of the men. Mens with the sme letter do not differ ccording to Fisher s LSD test t p > 0.05. Number of shoots per m 2 70 () Cirsium rvense L. 60 c bc 1000 900 c (b) Hordeum vulgre L. 50 40 30 20 10 b Ye r 2004 Yer 2005 800 700 600 500 b Yer 2004 Yer 2005 Fig. 3. The shoots density (plnts m -2 ) of Cirsium rvense L. () nd spring brley (Hordeum vulgre L.) (b) depending on soil compction. Brs denote the stndrd error of the men. Mens with the sme letter do not differ ccording to Fisher s LSD test t p > 0.05. Root weight (g m -2 ) 800 700 600 500 200 100 0 15 15 30 30 45 Soil depth (cm) () 45 60 Cirsium rvense L. 1.2 200 100 1.7 1.5 1.6 1.3 1.4 Soil dry bulk density (g cm -3 ) Root weight (g m -2 ) 350 250 200 150 100 50 0 15 15 30 30 45 Soil depth (cm) (b ) 45 60 159 Hordeum vulgre L. 200 150 100 50 1.8 1.7 1.6 1.5 1.4 1.3 Soil dry bulk densit l y (g cm -3 ) Fig. 4. Predicted nd rel vlues of root mss of Cirsium rvense L. () nd spring brley (Hordeum vulgre L.) (b) depending on soil bulk density nd soil depth. Eqution to the root weight of C. rvense L.: g m -2 = 12189.0 296.5x 112.9y; brley: g m -2 = 6888.5 53.5x 65.5y
Reintm, E. et l. Cirsium rvense on rble soils Soil depth (cm) 0 5 10 15 20 25 30 35 40 45 50 55 0 5 10 15 20 25 30 35 40 45 50 55 0 5 10 15 20 25 30 35 40 45 50 55 Hordeum vulgre L. Cirsium rvense L. 2006 Residul effect 2004 2005 0 1 2 3 4 5 6 7 8 Soil penetrtion resistnce (MP) Fig. 5. Direct effect (, b) nd residul effect (c) of soil compction nd Cirsium rvense L. nd spring brley (Hordeum vulgre L.) growing on soil penetrtion resistnce (MP). Brs denote stndrd error of the men. () (b) (c) were detected t the soil depth of 60 cm. The opposite occurred to the root mss of C. rvense, which in compcted soil incresed in depths 15 30 cm (Fig. 4). The root mss of C. rvense ws, in comprison with the root mss of brley, 2.8 times greter in upper soil lyers (15 cm) nd 2 times greter in deeper lyers. The results in the field experiment confirm the hypothesis tht C. rvense roots re ble to penetrte nd loosen compcted soil. Soil penetrtion resistnce, in the first yer fter plnting with direct compction, ws higher underneth C. rvense thn under brley in both compction tretments (Fig. 5). The yer fterwrds, C. rvense hd significntly reduced soil resistnce in the upper 30 cm soil lyer (Fig. 5b) even if the moisture content t the moment of mesure ws lower thn in yer 2004 (Tble 2). There ws trend of soil resistnce reduction in the deeper soil lyers underneth C. rvense, but the differences were not sttisticlly significnt. Compction incresed soil dry bulk density from 1.4 to 1.58 g cm -3 nd from 1.52 to 1.56 g cm -3 by brley cultivtion in topsoil (0 30 cm) s well s in subsoil (30 50 cm), respectively, in yer 2004 (Fig. 6b). Fifth yer continuous compction incresed soil bulk density especilly in subsoil by brley cultivtion. However, under C. rvense the soil bulk density remined lower in topsoil nd higher in subsoil in the first yer (Fig. 1). Second yer C. rvense growth incresed bulk density in topsoil nd decresed in subsoil. Residul effect Whet grown in rottion yer fter C. rvense showed greter shoot mss nd density formtion thn fter brley monoculture (Fig. 7). The differences were significnt increse on the previous yer s compcted soil, when the shoot mss of whet ws 1.5 times higher ginst the bckground of C. rvense thn ginst the bckground of brley (Fig. 7); lso the shoot mss of whet ws greter on un-compcted soil fter C. rvense thn fter brley. Whet shoot density ws 2 times greter following C. rvense on compcted nd un-compcted soil (Fig. 7b) wheres there 160
Vol. 17 (2008): 153 164. Soil dry bulk density (g cm -3 ) 1.70 1.65 () (b) 1.60 1.55 1.50 1.45 1.40 1.35 2004 2005 2006 Cirsium rvens e L. 2004 2005 2006 Hordeum vu lgre L. 0-30 cm 30-50 cm Fig. 6. Direct effect (2004 2005) nd residul effect (2006) of soil compction nd Cirsium rvense L. () nd spring brley (Hordeum vulgre L.) (b) growing on soil dry bulk density (g cm -3 ). Brs denote stndrd error of the men. Shoots weight (g m -2 ) () 420 380 360 340 320 280 b b 260 Cirsium rvense rvense L.res idul effect L. Hordeumvulgre L. residul effect Ho rdeum vu lgrel. residul effect effect c Number of shoots per m 2 (b) 900 c 800 700 600 500 b Cirsium rsiumrvensel. rvense residul effe L. Hordeum vulgrel. residul effecthordeumvulgrel. residul residuleffect effect Fig. 7. Residul effect of Cirsium rvense L. nd spring brley (Hordeum vulgre L.) on spring whet (Triticum estivum L.) shoots dry weight () nd density (b). Brs denote the stndrd error of the men. Mens with the sme letter do not differ ccording to Fisher s LSD test t p > 0.05. were no significnt differences in whet shoot density between compcted nd un-compcted soil fter brley. The residul effect on the grin yield of whet differed fr more thn shoot mss between the two tretments (Tble 5). Grin yield vried from 154 g m -2 to 248 g m -2 fter brley nd from 247 g m -2 to 345 g m -2 following C. rvense on compcted nd un-compcted soil, respectively. There were less thn 0.2 C. rvense plnts per m 2 in yer 2006 nd no negtive impct on whet yield ws detected. Mesures of soil penetrtion resistnce in the yer following C. rvense nd brley showed low- Tble 5. Residul effect of Cirsium rvense L., spring brley (Hordeum vulgre L.) nd soil compction on whet (Triticum estivum L.) grin yield (ir dry). Tretment Grin yield (g m -2 ) Residul effect of C. rvense un-compcted 345 2 compcted 247b Residul effect of brley un-compcted 248b compcted 154c 1 LSD 0.05 124 1 Lest significnt difference t p < 0.05 2 Mens with the sme letter do not differ ccording to Fisher s LSD test t p > 0.05 161
Reintm, E. et l. Cirsium rvense on rble soils er results in soil plnted previously by C. rvense, in both the topsoil nd the subsoil (Fig. 5c). Soil penetrtion resistnce fter C. rvense in topsoil ws 2 MP nd 1.5 MP lower in topsoil nd subsoil, respectively, thn fter brley. Due to the very dry seson (Tble 3), the vlues of bulk density were higher or lmost the sme in 2006 s in yer 2005 (Fig. 6, 2006). However, soil bulk density remined lower ginst the bckground of C. rvense thn brley. Discussion The loosening effect of compcted soil by C. rvense growing ws directly connected with its root system (more thn 1000 g m -2 ) nd this effect while evident in the first yer (2004) of C. rvense, ws especilly evident in the second yer (2005). The root system of C. rvense cn be extensive ccording to the literture, growing horizontlly s much s 6 m in one seson. Most ptches spred t the rte of 1 2 m per yer (Amor nd Hrris 1975). Roots of young C. rvense plnts cn grow rpidly, ccording to Ndeu nd Vnden Born (1989) whose reserch indicted growth rtes in the first 13 weeks of up to 1 cm per dy; nd fter just 18 weeks, plnts verged 26 boveground shoots, 154 underground shoots, nd 111 m of roots. There were, in this study, more C. rvense shoots on compcted soil in the second yer of growing. It indictes tht on compcted soil C. rvense ws developing more shoots thn on un-compcted soil nd lso root nlyses showed better root development nd higher mss in compcted thn un-compcted soil. At the sme time C. rvense does not tolerte strong direct compction. Soil compction, in n erlier study by 17 tonne trctor in six psses decresed the shoot weight of nturlly developed C. rvense by up to 50%, but did not totlly destroy the plnt (Reintm 2000). Newly plnted C. rvense developed shoots for the following spring, t density of 55 m -2 on un-compcted nd 88 m -2 on hevily compcted soil (Kuht nd Reintm 2001). Although trctor with lower weight (4.9 tonne) ws used in the current experiment, the development of C. rvense shoots ws similr to the erlier study. Donld (1994) reported tht shoot density nd root growth re closely correlted: res with highest shoot density lso hve the highest underlying root biomss nd the highest density of dventitious root buds, nd lso deeper roots. The most extensive root growth occurs on moist cly wheres growth is reduced on excessively wet soils, nd on droughty soils including snd, grvel, nd hrd-pns (Donld 1994). One explntion for there being more roots in compcted soil compred to un-compcted is tht the soil wter holding cpcity of the former is closer to cly soils nd the most extensive root growth occurs in moist cly. However, even if C. rvense does not tolerte hrd-pns it ws ble to spred its roots in compcted soil since the soil bulk density nd penetrtion resistnce in compcted soil were still probbly within the limit of tolernce of C. rvense. Most plnt roots cn not penetrte soil density in excess of 1.9 g cm -3 nd when the density is more thn 2.0 g cm -3 the plnts re not ble to use the soil wter (Konoplev, 1966). One-time cutting of C. rvense, t the sme time s the brley hrvesting in August, ws nother fctor tht led to n increse in C. rvense s density. Grekul nd Bork (2007) discovered tht one-time mowing filed to provide long-term control of C. rvense, nd ctully incresed shoot densities. Cutting stimulted the growth of C. rvense shoots most likely from the relese of dormnt dventitious root buds, nd led to mrked increse in C. rvense biomss by the second yer when ccompnied by fertiliztion. Survey in rble fields reveled tht soil penetrtion resistnce ws lower only underneth C. rvense ptches becuse most C. rvense roots cn be found directly below the bove-ground shoots, with little extension beyond the border of ptch (Donld 1994). However, the grin yield t the centre of dense C. rvense ptches cn rnge from 28 71% of the yield in djcent weed-free plots (McLennn et l. 1991). The sme ws estblished during this survey in Estonin rble fields. 162
Vol. 17 (2008): 153 164. The clones on most investigted fields were formed by vegettive spreding but lso by seeds. The expnsion by seeds ws evident in Helme, where C. rvense covered lmost ll the territory of the field nd no individul ptches were detected, ot density ws sprse or non-existent. Seeds ply n importnt role in the infesttion of new fields previously free of C. rvense. Grgli et l. (2006) found tht n extensive root system nd the bility to form new eril shoots result in dense ptches only few yers fter estblishment. The spred of C. rvense by seeds ws especilly evident in the second hlf of 1990s in Estoni, when t the end of August the ir ws full of C. rvense plume. During tht time C. rvense ws clled Estonin cotton due to its mssive spred on fllow lnd. The soil loosening effect of C. rvense roots is connected with the formtion of biopores nd orgnic mtter fter the deth of living roots. The biopores formed from plnt roots my be more stbile thn biopores formed by erthworms (Mc Kenzie nd Dexter 1988). Blckwell et l. (1990) detected tht biopores formed from lucerne roots tht hve dimeter over 4 mm cn tolerte more thn 200 kp pressures. Hirth et l. (1997) found, however, tht only 6% of the roots of ryegrss tht were deflected sidewys, met with holes in the compcted subsoil. The number of roots tht met with holes filled with either csts or soil ws not significntly different from the number of roots tht met with empty holes. Ded plnt roots lso increse the content of orgnic mtter in soil nd with tht the resistnce to the compction increses. The increse of orgnic mtter up to 5 g kg -1 in cly soils decresed soil bulk density by 0.06 g cm -3 (Quirog et l. 2000). The root weight of C. rvense, in the current study, rnged between g m -2 in the top 30 cm soil lyer, nd between 100 200 g m -2 in deeper soil. The root mss of brley vried between 100 150 g m -2 in topsoil nd less thn 50 g m -2 in subsoil (Fig. 4). This showed tht C. rvense left more orgnic mtter in the soil thn brley. Conclusion The results reveled significntly lower soil penetrtion resistnce nd bulk density underneth C. rvense thn under crops in Estonin soils ffected by C. rvense over four yers. C. rvense tolerted better soil compction nd its shoot nd root mss ws less ffected by soil compction thn ws the shoot nd root mss of brley. Due to the influence of C. rvense roots, soil penetrtion resistnce nd soil bulk density were lower in un-compcted nd compcted soil under C. rvense thn under crops. Whet yield ws higher fter C. rvense ginst the bckdrop of both compction tretments due to the lower soil penetrtion resistnce nd bulk density in these tretments. The conclusion my be drwn tht in res ffected by deep-rooted weed species, such s C. rvense, soil physicl properties my improve in lredy the first two yers. How much C. rvense cn we tolerte on field nd how much C. rvense we need to improve soil chrcteristics needs further investigtions. Acknowledgments. This reserch ws supported by Estonin Science Foundtion grnt No 5418 nd 7622. The English correction of the pper ws mde by Mrcus Denton from LLC Derettens. References Amor, R.L. & Hrris R.V. 1974. Distribution nd seed production of Cirsium rvense (L.) Scop. in Victori, Austrli. Weed Reserch 14:317 323. Astover, A., Roostlu, H., Luringson, E., Lemetti, I., Selge, A., Tlgre, L., Vsiliev, N., Mõtte, M., Tõrr, T. & Penu, P. 2006. Chnges in griculturl lnd use nd in plnt nutrient blnces of rble soils in Estoni. Archives of Agronomy nd Soil Sciences 52: 223 231. Blckwell, P.S., Green, T.W. & Mson, W.K. 1990. Responses of biopore chnnels from roots to compression by verticl stress. Soil Science Society of Americ Journl 54: 1088 1091. Donld, W.W. 1994. The biology of Cnd thistle (Cirsium rvense). Reviews of Weed Science 6: 77 101. FAO, ISSS, ISRIC 1998. World reference bse for soil resources. World Soil Resources Rep. 84, Rome. FAO 2000. Soil nd terrin dtbse, soil degrdtion sttus nd soil vulnerbility ssessment for Centrl 163
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