Weed seed bank density and composition in a tillage and landscape variability study

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1 Communictions in iometry nd Crop Science Vol. 6, No. 1, 2011, pp Interntionl Journl of the Fculty of griculture nd iology, Wrsw University of Life Sciences, Polnd REGULR RTICLE Weed seed bnk density nd composition in tillge nd lndscpe vribility study Jessic. Kelton 1, ndrew J. Price 2 *, Edzrd vn Snten 1, Kipling S. lkcom 2, Frncisco J. rrig 2, Joey N. Shw 2 1 Deprtment of gronomy nd Soils, uburn University, uburn, lbm, United Sttes. 2 United Sttes Deprtment of griculture, griculturl Reserch Service, Ntionl Soil Dynmics Lbortory, uburn, lbm, United Sttes. * Corresponding uthor: ndrew J. Price E-mil: ndrew.price@rs.usd.gov CITTION: Kelton, J.., Price,.J., vn Snten, E., lkcom, K.S., rrig, F.J., Shw, J.N. (2011). Weed seed bnk density nd composition in tillge nd lndscpe vribility study. Communictions in iometry nd Crop Science 6 (1), Received: 6 pril 2010, ccepted: 23 Mrch 2011, Published online: 5 pril 2011 CCS 2011 STRCT Reserch hs shown tht weed communities re influenced by mny fctors including cropping systems, tillge prctices, nd geogrphicl lndscpe. Evluting response of the weed seed bnk to vrying griculturl prctices nd lndscpe positions cn led to better site-specific weed control strtegies. Therefore, the objective of this study ws to evlute cropping nd lndscpe ffects on weed seed bnk composition nd density. Soil smples were collected from n estblished experiment locted t the E.V. Smith Reserch nd Extension Center ner Shorter, L. The tretment design ws fctoril rrngement of two tillge systems (conventionl nd no-till), two mnure (with nd without), nd three lndscpe positions, in corn (Ze mys L.) cotton (Gossypium hirsutum L.) rottion. greenhouse study ws conducted using soil smples from the experiment to identify weed seedlings from ech tretment. Results from this experiment indicte tht the inclusion of high residue cover crops into conservtion tillge system cn reduce weed seed within the upper 7.6 cm of the soil seed bnk. Key Words: conservtion tillge; cover crops; seed bnk dynmics; seedling recruitment. INTRODUCTION Successful weed mngement methods re n integrl prt of productive griculturl systems. Reserch hs shown tht weed communities re influenced by vrious fctors (uhler et l., 2000; Crdin et l., 2002); consequently, weed mngement prctices will differ under vrying griculturl systems nd lndscpes. Understnding how nd to wht

2 22 Communictions in iometry nd Crop Science, 6(1) extent environmentl fctors nd cropping system methods ffect weed popultion dynmics imprts further knowledge with which to combt problemtic weed communities. s the use of conservtion tillge systems increses becuse of soil nd moisture benefits (Tubbs nd Gllher, 2000; Sini et l., 2006), weed control from tillge, in conventionl systems is being replced by chemicl weed suppression. Greter inputs of herbicides re required due to incresed weed densities in reduced tillge systems compred with conventionl systems (Crdin et l., 2002; Sosnoskie et l., 2006). The use of winter cover crops is common prctice in conservtion tillge systems throughout the southestern United Sttes becuse of vrious environmentl nd griculturl benefits (Reeves et l., 2005). Previous reserch suggests tht one of the dvntges of high residue cover crop integrtion into n griculturl system is the bility to suppress winter nd erly-seson weeds through physicl nd chemicl mens (árberi nd Mzzoncini, 2001; Sini et l., 2006). The llelopthic effects of some cover crop residues my lso provide mesure of winter s well s erly-seson summer weed suppression in crop production. Vritions in topogrphy hve often been relted to fluctuting crop yields (Terr et l., 2006). Krvchenko nd ullock (2000) reported negtive correltion between elevtion nd yield during periods of low rinfll; during wet periods there ws positive correltion. These studies hve been limited to lndscpe vribility effects on crop yields; however, weed popultions could be expected to respond in kind. Weed popultions hve been determined to differ sptilly throughout field under vrying conditions (Dielemn et l., 2000). In this study, we ttempt to understnd the reltionship between the weed seed bnk nd multiple griculturl mngement prctices nd lndscpe positions. We lso hope to gin knowledge pertining to weed seed bnk dynmics in conservtion tillge systems compred with conventionlly tilled griculturl lnd. MTERILS ND METHODS FIELD SITE DESCRIPTION ND EXPERIMENTL PPROCH Soil cores were collected in 2006 from n estblished experiment (Terr et l., 2006) locted on 9-h Costl Plin field t the lbm griculturl Experiment Sttion s EV Smith Reserch Center in Shorter, lbm. Soils t the field site mostly clssify s fine nd fine-lomy, siliceous, subctive, thermic Typic, Oxyquic nd quic Pleudults (Terr et l., 2006). Experimentl methods were described by Terr et l. (2006). The tretment design ws fctoril rrngement of two tillge systems [conventionl (CT) nd no-till sub-soiling (NT)] with nd without mnure pplictions of pproximtely 10 Mg h -1 yr -1 nnully nd three lndscpe positions determined by Terr et l. (2006) (summit, dringe wy, nd side slope). The conventionl tillge systems consisted of fll chisel plowing nd disking followed by field cultivtion nd in-row subsoiling in the spring 2 to 3 weeks prior to plnting. corn-cotton rottion with both phses of the rottion present ech yer ws used in the experiment. Six replictes were imposed on 6.1 m by 240 m long strips cross the field. Ech strip in the field ws divided into 6.1 m by 18.3 m cells. Conventionl tillge systems were prepred with fll plowing nd disking followed by cultivtion nd in-row sub-soiling to 40 cm with KMC1 ripper, prior to spring sowing. The conservtion tillge systems received only in-row sub-soiling in the sme wy s conventionlly tilled plots. Conservtion tillge plots were sown in mixture of crimson clover (Trifolium incrntum L.), fodder rdish (Rphnus stivus L.), nd white lupin (Lupinus lbus L.) prior to corn nd rye (Secle cerele L.) nd blck ot (ven strigos Schreb.) mixture before cotton. Termintion of cover crops t nthesis ws ccomplished by glyphoste t 1 kg h -1 of isopropylmine slt followed by mechnicl roller.

3 Kelton et l. Weed seed bnk in tillge nd lndscpe vribility study 23 DT COLLECTION ND GREENHOUSE PROCEDURES Five soil cores, ech with rdius of 3.8 cm, were tken, to depth of 15.2 cm, from ech of 72 cells representing 3 replictes of ll tretment combintions. The soil cores were then divided into two depths (0-7.6 cm nd cm). Following the methods of Crdin nd Sprrow (1996), smples were wshed nd sieved to brek up soil clods nd remove lrge debris. Ech smple ws then plced in 28 x 28 x 5 cm plstic flt on top of snd bed in n enclosed greenhouse nd wtered dily. Tempertures were set for dy/night vlues of 25 nd 22 C respectively. s weed seedlings emerged nd were identified they were counted nd removed from the flts. Seedling identifiction nd removl continued periodiclly in this mnner for pproximtely 5 months until seedling emergence cesed. t this point, soil smples were individully bgged in 3.7-L plstic bgs, which were stored in cooler t 3 C for three months to simulte winter tempertures. Smples were then returned to flts in the greenhouse under the sme conditions. During this second greenhouse period, weed seedling counts continued for pproximtely four months until seedling emergence hd cesed. DT NLYSIS reltive importnce (RI) index vlue, or reltive bundnce vlue, ws clculted for individul species in ech plot to describe the occurrence of weed species (Tble 1). Dt nlysis proceeded with seprte nlysis for ech depth using mixed models procedures s implemented in SS PROC GLIMMIX. Weed seed density (seed m -2 ) required the lognorml distribution to rrive t normlly distributed residuls, wheres species richness (S), evenness (J), nd diversity (H ) were nlyzed using norml distribution function. Fctors tillge, lndscpe position, mnure, nd crop, nd their interctions were considered to be min effects, wheres block from the originl experiment (Terr et l., 2006) ws the lone rndom effect. RESULTS SPECIES COMPOSITION We identified 19,087 individul seedlings in this experiment, which belonged to 19 fmilies; totl of 32 species (27 nnul, 4 perennil, nd 1 nnul/biennil) were present (Tble 1). The six mjor weeds were henbit (Lmium mplexicule L.) (15,376), common chickweed [Stellri medi (L.) Vill.] (851), nnul bluegrss (Po nnu L.) (739), smllflowered bittercress (Crdmine perviflor L.) (587), crpetweed (Mollugo verticillt L.) (539), nd purple cudweed [Gmochet purpure (L.) Cbrer] (398). WEED SEED DENSITY Weed seed density dt nlysis indicted tht there were significnt (P ) differences mong min effect levels for tillge, mnure ppliction nd in the 0 - to 7.6-cm depth rnge (Tble 2). Summit nd side slope weed densities differed t simultion djusted (P = ). The differences for the deeper soil cores indicted tht crop did not ply role (P = ) but the summit zone differed from the other two zones t (P 0.099; Tble 3). Men weed seed density for the no-till plots ws 23,220 seeds m -2 nd 53,978 seeds m -2 for the conventionlly tilled plots in shllow core smples; in deeper core smples, there ws 859 seeds m -2 in no-till tilled nd 14,127 seeds m -2 in conventionlly tilled plots, showing the tendency of conventionl tillge to trnsport weed seed down the soil profile. ddition of mnure to plots incresed seed density t both soil core depths, lthough there were five times s mny weeds seeds in the top 7.6 cm thn were t the lower soil depth with mnure ddition (46,240 vs. 8,048 seeds m -2 ). Corn plots hd 42,587 seeds m -2 t the shllow depth compred to 29,431 seeds m -2 for cotton; densities were n order of mgnitude lower in the deep cores nd not significntly different between crops.

4 24 Communictions in iometry nd Crop Science, 6(1) Tble 1. Seed bnk weed species composition nd reltive bundnce. Ltin Nme Common Nme yer code Life history* Reltive bundnce mrnthus spp. mrnthus spp. M** 0.16 Cpsell burs-pstoris (L.) Medik. Shepherd s purse CPP W 0.82 Crdmine prviflor L. Cerstium fontnum ssp. vulgre (Hrtmn) Greuter & urdet Chenopodium lbum L. Smllflowered bittercress CRP W 3.07 Mouseer chickweed CERVU W 0.08 Common lmbsqurters CHEL S 0.04 Conyz cndensis (L.) Cronq. Horseweed ERIC 0.01 Coronopus didymus (L.) Sm. Lesser swinecress COPDI W 0.75 Dctyloctenium egyptium (L.) Willd. Crowfootgrss DTTE S 0.01 Digitri ciliris (Retz.) Koel. Southern crbgrss DIGSP S 0.01 Eleusine indic (L.) Gertn. Goosegrss ELEIN S 0.19 Ergrostis cilinensis (ll.) Vign. ex Jnchen Stinkgrss ERCN S 0.02 Euptorium cpillifolium (Lm.) Smll Dogfennel EUPCP P 0.02 Chmesyce mcult L. Smll Spotted spurge EPHM S 0.20 Gernium crolininum L. Crolin gernium GERC W 0.06 Gmochet purpure (L.) Cbrer Purple cudweed GNPU / 2.10 Jcquemonti tmnifoli (L.) Griseb. Smllflower morningglory IQT S 0.01 Lmium mplexicule L. Henbit LMM W Melochi corchorifoli L. Redweed MEOCO 0.08 Mollugo verticillt L. Crpetweed MOLVE S 2.92 Nuttllnthus cndensis (L.) D.. Sutton Oenother lcinit Hill Oldfield todflx Cutlef eveningprimrose OEOL W 0.06 Oxlis strict L. Yellow woodsorrel OXST P 0.01 Physlis ngult L. Cutlef groundcherry PHYN 0.03 Po nnu L. nnul bluegrss PON W 3.87 Polypremum procumbens L. Rustweed POEPR P 0.03 Sisyrinchium rosultrum ickn. lue-eyed grss W 0.01 Spergul rvensis L. Corn spurry SPRR 0.24 Stellri medi (L.) Vill. Common chickweed STEME W 4.45 Triodnis perfolit (L.) Nieuwl. vr. biflor (Ruiz & Pvon) rdley Smll venuslookingglss TJDI W 0.01 Urochlo texn (uckl.) R. Webster Texs millet URTE2 S 0.02 Vernoni gluc (L.) Willd. rodlef ironweed P 0.01 Veronic peregrin L. Purslne speedwell VERPG W 0.37 *, nnul; W, winter nnul; S, summer nnul; P, perennil; /, nnul or biennil. Life histories were determined by Rdford et l. (1968).

5 Kelton et l. Weed seed bnk in tillge nd lndscpe vribility study 25 Tble 2. Men seed density for ech tretment within the upper soil core smples (0-7.6-cm). Dt were nlyzed using lognorml distribution function, hence confidence intervls re provided for the bck-trnsformed mens to indicte the precision of the estimte. Simultion djusted P-vlue vs. Fctor Level Count 90% CI Level 2 Level 3 Seeds m -2 Tillge Non-inversion 23,220 (18936, 28473) Conventionl 53,978 (43564, 66879) Mnure Yes 46,240 (37507, 57005) No 27,106 (21991, 33409) Crop Corn 42,587 (34050, 53262) Cotton 29,431 (24201, 35790) Zone Summit 40,554 (31859, 51620) Dringe wy 40,074 (30297, 53004) Side slope 27,304 (21455, 34746) Tble 3: Men seed density for ech tretment within the lower soil core ( cm) smples. Dt were nlyzed using lognorml distribution function, hence confidence intervls re provided for the bck-trnsformed mens to indicte the precision of the estimte. Simultion djusted P-vlue vs. Fctor Level Count 90% CI Level 2 Level 3 Seeds m -2 Tillge Non-inversion 859 (304, 2417) Conventionl 14,127 (5049, 39522) Mnure Yes 8,048 (2867, 22581) No 1,508 (536, 4238) Crop Corn 3,000 (1071, 8398) Cotton 4,045 (1430, 11435) Zone Summit 5,245 (1798, 15287) Dringe wy 5,018 (1659, 15171) Side slope 1,606 (569, 4529)

6 26 Communictions in iometry nd Crop Science, 6(1) SPECIES RICHNESS, DIVERSITY, ND EVENNESS Species richness (S) ws influenced by lndscpe position nd mnure ppliction in soil cores down to 7.6-cm with mnure ppliction significntly incresing species richness nd dringe wy > summit > side slope (Tble 4). In deeper soil cores species, richness ws influenced by ll min effects except crop (Tble 5). There were significnt interctions for the 0 to 7.6 cm soil smples between lndscpe position nd tillge prctice s well s between lndscpe position nd crop (Fig. 1). While the rnking of summit nd slide slope reltive to ech other remined the sme between conventionlly tilled nd no-till plots, the dringe wy hd significntly higher species richness in conventionlly tilled plots. Species richness for side slope smples from no-till plots hd significntly lower species richness thn the two other zones. The zone x crop interction ws due to both chnges in rnk s well s mgnitude. Cotton plots from the dringe wy zone hd the highest species richness vlues. No significnt min effects were observed for species evenness (J) t either soil depths but there ws significnt interctions between tillge nd mnure ppliction in the upper soil cores s conventionl tillge pprently cused mixing of weed seed resulting t greter evenness when mnure ws pplied, wheres no significnt difference ws observed under no-till (Fig. 2). In the 7.6 to 15.2 cm soil cores, J ws lower in no-till plots when plnted to corn. Species diversity, s defined by the Shnnon-Wiener index (H ), ws significntly different for ll zones with dringe wy > summit > side slope (Tble 4). The rnking for H ws mintined in the deeper cores, but only side slope ws significntly different from the other two (Tble 5). Interctions occurred in the 0 to 7.6-cm soil cores between tillge nd lndscpe position s well s tillge nd mnure ppliction (Fig. 3). Dringe wy position hd the highest diversity index under conventionl tillge; under no-till tillge the side slope hd significntly lower index thn the other lndscpe positions (Fig. 3). The effect of mnure ppliction on H ws the opposite under no-till compred to conventionl tillge. Thus no brod generliztion of mnure ppliction on species diversity my be mde. b b b Figure 1. Species richness (S) from the 0 to 7.6 cm soil cores s determined by slope position nd tillge or crop. Mens within tillge or crop tretments with different letters re different t simultion djusted P 0.10.

7 Kelton et l. Weed seed bnk in tillge nd lndscpe vribility study 27 Tble 4: Clculted vlues for richness (S), evenness (J), nd the Shnnon-Wiener diversity index (H') for min tretments mong the 0- to 7.6-cm soil cores. Significnt differences between vlues within tretments t simultion djusted P < 0.10 re identified by different letter following the vlue. Tretment Richness (S) Evenness (J) Diversity Index (H') Tillge Conventionl Non-inversion SE Mnure Yes No 5.54 b SE Crop Corn Cotton SE Zone Summit 6.15 b b Dringe wy Side slope 4.10 c c SE Tble 5: Clculted vlues for richness (S), evenness (J), nd the Shnnon-Wiener diversity index (H') for min tretments mong the 7.6-to 15.2-cm soil cores. Significnt differences between vlues within tretments t simultion djusted P < 0.10 re identified by different letter following the vlue. Tretment Richness (S) Evenness (J) Diversity Index (H') Tillge Conventionl Non-inversion 2.04 b b SE Mnure Yes No 2.81 b SE Crop Corn Cotton SE Zone Summit 3.40 b Dringe wy Side slope 2.31 c b SE

8 28 Communictions in iometry nd Crop Science, 6(1) b Figure 2. Species evenness (J) from the 0 to 7.6 cm soil cores s determined by tillge nd mnure ppliction (left pnel) or from the cm soil cores s determined by tillge nd crop (right pnel). Mens within tillge or crop tretments with different letters re different t simultion djusted P b b Figure 3. Species diversity (H ) from the 0 to 7.6 cm soil cores s determined by tillge nd slope position or crop. Mens within tillge tretments with different letters re different t simultion djusted P RESULT IMPLICTIONS FOR WEED MNGEMENT Previous reserch hs noted species composition shifts in response to vrying tretments nd environmentl fctors (rberi nd Mzzoncini, 2001; Guretzky et l., 2005). Further reserch is needed to determine weed community trends bsed on tretments nd potentilly offer predictions of future weed species composition in the respective tretments, specificlly cover crop systems. Winter nd erly-seson summer weed seed density in this experiment sw significnt reduction in the shllow no-till sub-soiled plots where both clover nd rye cover crops were plnted when compred to conventionlly tilled plots. This finding grees with previous publictions tht demonstrted reduction in weed density when cover cropping is integrted into conservtion system (árberi nd Mzzoncini, 2001; Sini et l., 2006). Previous reserch reported incresed weed densities s tillge intensity ws reduced (Crdin et l., 2002; Sosnoskie et l., 2006). Other reserch reports different responses by individul species under vrying tillge prctices nd over time (Chhokr et l., 2007; Steckel et l., 2007). In these experiments, the reserch ws focused on determining the difference in seed bnk densities between reduced tillge nd conventionl tillge systems; no reserch reported the inclusion of high residue cover crops into reduced tillge prctices. Our

9 Kelton et l. Weed seed bnk in tillge nd lndscpe vribility study 29 findings, however, contrdict árberi nd Mzzoncini (2001) who found lower input systems with cover crops hd incresed weed seed densities in subsequent yers compred with conventionl systems. These results show tht the use of cover crops in reduced tillge systems my offer the potentil to dopt conservtion tillge system without n increse herbicide usge to keep overll weed density in check. Further reserch is needed to determine if long-term doption of cover crops could led to n eventul reduction in herbicide pplictions once the soil seed bnk hs been sufficiently depleted. CONCLUSIONS To conclude, determining how, nd to wht extent, weed communities re ffected by griculturl mngement systems is complex nd chllenging undertking. With ech new experiment, progress is mde towrd understnding how the griculturl community cn direct nd influence the weed seed bnk. In future, with greter insight, it is likely tht we will be ble to ccurtely predict nd pln for weed species nd species shifts in most griculturl settings. SOURCES OF MTERILS 1 KMC ripper, Kelly Mnufcturing Compny, 80 Vernon Drive, Tifton, G SS softwre, version 9.2, Sttisticl nlysis Systems Institute Inc. Cry, NC CKNOWLEDGMENTS The uthors wish to thnk Mr. Jrrod Jones, Mr. Json Wrd, Mr. Crl Mnnschreck, nd Mrs. Mri Stoll for their invluble ssistnce with smple collection nd project execution. REFERENCES árberi, P., Mzzoncini, M. (2001). Chnges in weed community composition s influenced by cover crop nd mngement system in continuous corn. Weed Science 49, uhler, D.D., Liebmn, M., Obrycki, J.J. (2000). Theoreticl nd prcticl chllenges to n IPM pproch to weed mngement. Weed Science 48, Crdin, J., Regnier, E., Hrrison, K. (1991). Long-term tillge effects on seed bnks in three Ohio soils. Weed Science 39, Crdin, J., Herms, C.P., Doohn, D.J. (2002). Crop rottion nd tillge system effects on weed seedbnks. Weed Science 50, Chh okr, R.S., Shrm, R.K., Jt, G.R., Pundir,.K., Gthl, M.K. (2007). Effect of tillge nd herbicides on weeds nd productivity of whet under rice-whet growing system. Crop Protection 26, Dielemn, J.., Mortensen, D.., uhler, D.D., Ferguson, R.. (2000). Identifying ssocitions mong site properties nd weed species bundnce. II. Hypothesis genertion. Weed Science 48, Guretzky, J.., Moore, K.J., rummer, E.C., urrs, C.L. (2005). Species diversity nd functionl composition of pstures tht vry in lndscpe position nd grzing mngement. Crop Science 45, Krvchenko,.N., ullock, D.G. (2000). Correltion of corn nd soyben grin yield with topogrphy nd soil properties. gronomy Journl 92, Rdford,.E., hles, H.E., ell, C.R. (1968). Mnul of the Vsculr Flor of the Crolins. Chpel Hill, NC: University of North Crolin Press. Reeves, W., Price,.J., Ptterson, M.G. (2005). Evlution of three cerels for weed control in conservtion-tillge nontrnsgenic cotton. Weed Technology 19,

10 30 Communictions in iometry nd Crop Science, 6(1) Sini, M., Price,.J., vn Snten, E. (2006). Cover crop residue effects on erly-seson weed estblishment in conservtion-tillge corn-cotton rottion. Proceedings of the 28th nnul Southern Conservtion Systems Conference. mrillo, TX, 26 28, June Sosnoskie, L.M., Herms, C.P., Crdin, J. (2006). Weed seed bnk community composition in 35-yr-old tillge nd rottion experiment. Weed Science 54, Steckel, L.E., Sprgue, C.L., Stoller, E.W. Wx, L.M., Simmons, F.W. (2007). Tillge, cropping system, nd soil depth effects on common wterhemp (mrnthus rudis) seed-bnk persistence. Weed Science 55, Terr, J.., Shw, J.N., Reeves, D.W., Rper, R.L., vn Snten, E., Schwb, E.., Msk, P.L. (2006). Soil mngement nd lndscpe vribility ffects field-scle cotton productivity. Soil Science Society of meric Journl 70, Tubbs, R.S. Gllher, R.N. (2005). Conservtion tillge nd herbicide mngement for two penut cultivrs. gronomy Journl 97,