喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請(qǐng)放心下載，，有疑問(wèn)咨詢(xún)QQ:414951605或者1304139763 ======================== 喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請(qǐng)放心下載，，有疑問(wèn)咨詢(xún)QQ:414951605或者1304139763 ======================== Effects of a new wide-sweep opener for no-till planter on seedzone properties and root establishment in maize (Zea mays, L.):A comparison with double-disk openerT. Vameralia, M. Bertoccob,*, L. SartoribaDipartimento di Agronomia Ambientale e Produzioni Vegetali, University of Padova, Agripolis,Viale dellUniversita 16, 35020 Legnaro, Padova, ItalybDipartimento Territorio e Sistemi Agro-forestali, University of Padova, Agripolis,Viale dellUniversita 16, 35020 Legnaro, Padova, ItalyReceived 17 February 2005; received in revised form 13 July 2005; accepted 29 July 2005AbstractAccording to the kind of opener applied, no-tillage seeders can variously modify soil physical properties in relation to soiland climate conditions, thus potentially affecting crop emergence and early growth.The technological evolution of seeders for direct drilling of arable crops, progressively achieved in recent years, has beenconsiderable, but new improvements now available need to be individually tested. In a field trial at Udine (NE Italy), the effectsofanewkindofwide-sweepopener(i.e.,sidecoulterscurvedupwardsintheirfinalpartandslightlyangledtowardsthedirectionof work) on soil physical properties in the seed zone and on crop emergence and early root growth of maize were evaluated infour different soils over a 2-year period (20022003), in comparison with the widely used double-disk opener.With respect to the double-disk opener, ingeneral thewide-sweep type led to higher soilresidue mixingwithout excessivereduction of the soil-covering index being observed, ?27 and ?6%, respectively. The wide-sweep opener also showed lowerbulk density and soil penetration resistance in the top 5-cm soil layer of the seed furrow, although no greater root length densitywas found in maize at the three-leaf stage, probably due to the smoothing effect caused by the side coulters at the seeding depth.Acertaindelayinplantemergenceinsomecaseswasalsorevealedforthewide-sweepopener,whichmayberelatedtothelowersoil/seed contact.Deviations from this general behaviour in the various soils (texture and initial conditions) are discussed.# 2005 Elsevier B.V. All rights reserved.Keywords: Maize; No-tillage; Opener type; Root growth; Seed zone physical & Tillage Research 89 (2006) 196209Abbreviations: CI, covering index; DAS, days after sowing; DDO, double-disk opener; FRSD, furrow roughness standard deviation; PR,penetration resistance; RI, residue incorporation; RLD, volumetric root length density; SOC, soil organic carbon; WSO, wide-sweep opener* Corresponding author. Tel.: +39 049 8272723; fax: +39 049 8272774.E-mail address: matteo.bertocco.1unipd.it (M. Bertocco).0167-1987/$ see front matter # 2005 Elsevier B.V. All rights reserved.doi:10.1016/j.still.2005.07.0111. IntroductionIn the last few years, the economic and environ-mental implications of conventional tillage, such aserosion, compaction and inverting soil layers, have ledto re-examination of no-tillage even in Italy (Sartoriand Peruzzi, 1994). Especially, in the heavy soils ofthis country, deep ploughing aims at increasing soilporosity, at least temporarily, in order to createsuitable conditions for both seed germination and rootgrowth. Simplification of weed management andhigher grain yields of summer crops like maize aregenerally achieved with respect to no-tillage, asevidencedbythefewdataavailableintheliteratureforItaly (e.g., Bona et al., 1995).The performance of no-tillage seeders depends onseveral factors related to field conditions, includingtype and amount of residues at soil surface, openerdesign (Morrison, 2002) and the crop to be sown. Theimplementsoftheseseedersmusthavehighflexibility,so that various crops can be sown in differing fieldconditions with correct seed deposition (e.g., density,distance, depth). In no-tillage practices, the character-istics of the seed-furrow play an important role ingermination. Many authors have pointed out that themost significant factors regulating germination, suchas soil matric potential, temperature (Lindstrom et al.,1976; Schneider and Gupta, 1985) and sowing depth(Alessi and Power, 1971; Mahdi et al., 1998) areaffected by the soil/opener interaction (Tessier et al.,1991a,b). In particular, in order to maintain constantsowing depth, various types of linkages betweenopener and seeder toolbar have been proposed duringthe last few decades. For instance, connection with aspring system, the oldest but simplest solution, is notalways adequate to guarantee uniformity of sowingdepth, especially in heavy soils. Great improvementshave been obtained with parallel linkage, since thisallows the opener to follow soil surface profilesaccurately.Many of the characteristics of the seed zone in no-tillage depends on the type of opener attached to theseeder (Wilkins et al., 1983) and the two main typesused tine and disk may lead to great differences.The tine opener typically creates an appreciablebursting effect in the soil and generally moves aconsiderable quantity of fine damper aggregatestowardsthesoilsurfaceafactparticularlyappreciablein tools having an asymmetric shape (Darmora andPandey, 1995) but which may be negative if a rainlessperiodoccurs aftersowing,assoildryingisaccelerated(Chaudhuri, 2001). In similar conditions, the diskopener may cause more progressive water loss inthe soil layer above the seeds than the tine opener(Tessier et al., 1991a,b), although great drawbacks areobservable in wet clay soils because a permanentunclosed furrow is commonly created (Sartori andSandri, 1995).It is widely recognised that management of cropresidues (previous crop) is one of the most importantconstraints for adopting no-tillage (Carter, 1994). Tineopenersshiftorganicdebrisinthesoilsurfacefromthecrop row sideways, with possible plugging of theseeder in the case of heavy residues, whereas diskopeners may lead to hairpinning, with a consequentbad soil/seed contact and possible toxic effect onseedlings (Hultgreen, 2000). Unmanaged residues cancreate many problems in direct sowing, but theirpresence at the soil surface is generally beneficial inlimiting some negativeeffects on soil, like erosion andwater losses (Gill and Aulakh, 1990).As regards soil and climate conditions, openersshould achieveseveral aims, like uniformityof sowing i.e., spacing and depth production of a suitableamount of fine soil aggregate to ensure soil/seedcontact, reduction of water losses, avoidance of seedcontact with either fertilizers or crop residues andlimitation of furrow compaction, which may obstructroot growth (Willatt, 1986; Tsegaye and Mullins,1994; Bueno et al., 2002). The type of opener wasfound to affect emergence and plant establishmentmarkedly (McLeod et al., 1992), especially in crust-forming soils, for which better results are generallyobtained with the double-disk opener (Hemmat andKhashoei, 2003).The technological evolution of no-tillage seedersfor arable crops, progressively achieved in this sector,has been great, but the large number of improvementsnow available must be individually tested and care-fully evaluated. In addition, much of the literature onthis subject refers almost exclusively to opener/soilinteractions, without analysing effects on crop growth.The effects of furrow shape and its properties on thedraft force required by different opener types havebeen widely studied in relation to soil conditionsand operating parameters, such as depth or speedT. Vamerali et al./Soil & Tillage Research 89 (2006) 196209197(Gebresenbet and Jo nsson, 1992; Collins and Fowler,1996; Sa nchez-Giro n et al., 2005). Instead, only a fewstudies have examined some crop parameters and theygenerally deal with drills for autumn sowing ofcereals. For instance, Chaudhry and Baker (1988)found that various types of opener led to differenttypes of growth of barley seedlings, i.e., greater shootand root weights when both winged (T-shaped groove)or hoe (U-shaped groove) types are used instead of thetriple-disk one.In this framework, the present study evaluates theperformance of an innovative wide-sweep opener,linked to the frame by a double linkage unit. Its effectson some soil physical properties in the seed zone, cropemergence and early root growth of maize wereevaluated in various soils over a 2-year period in NEItaly and compared with those of a double-diskopener, which is the most widespread in Italy.2. Materials and methods2.1. Description of equipmentThe performances of a new wide-sweep opener(WSO) with which the no-till air seeder Cerere(Tecnoagricola, Udine, Italy) has been equipped, wascompared with that of a double-disk opener (DDO)adopted by the no-till planter Max Emerge 2 (JohnDeere Italia, Milan, Italy).The WSO has a straight axis, ending with a frontchisel and two rear side 18-cm wide coulters, whichare slightly angled towards the direction of work andcurved upwards (908) in their final part (25 mm high)(Fig. 1). The front chisel cuts soil 2530 mm deeperthan the coulters. Seed delivery to each unit is througha single pneumatic tube from the centralised volu-metric metering system, which allows the seeder toassume a certain degree of polyvalence. Althoughvarious types of deposition (i.e., row spacing) can beset, in our field trial as the first test of this prototypeopener maize was sown in rows 0.45 m apart, adistance commonly used in the experimental site.The structure of the seeder equipped with the WSOincludes one rigid and one folding frame. The first issupported by a front head-shaft to couple the seeder tothe tractor and two rear low-pressure wheels fortransport. The folding frame aims at guaranteeing thatthe soil profile can be followed by the openers asregularly as possible. For this reason, it has threeindependent jointed sections, each 1.5 m wide andlinked to the rigid frame with four elastic joints. Eachsection has five openers, for a total of 15 sowing rows,which are laid on three seeding lines and equippedwith a single parallel linkage for improved stability. Inaddition, each section is supported by a front wheeland a rear packer tandem (Fig. 2). The latter is anessential component for the working the seeding unitin this seeder; it is made of 10 wheels per section, with3.508 tyres and 0.9 bar pressure.The seeder equipped with the DDO is an eight-unitmounted no-till planter with pneumatic seed meteringand 0.75 m row spacing, resulting in a 6 m workingwidth. The DDO used here is composed of a single,fluted,round-bladedcoulterandadouble-disk,associated with two side rollers and two rear V-mounted wheels (Fig. 2).Performance valuation of opener types requiresdifferences among seeders to be kept to a minimum,although this is not always completely possible,T. Vamerali et al./Soil & Tillage Research 89 (2006) 196209198Fig. 1. Sketch of wide-sweep opener (WSO) attached to Cerere no-till air seeder: (a) front chisel; (b) side coulter; (c) end of coulter(curved upwards); (d) multiple seed dispenser; (e) part of parallellinkage.especially when opener design differs greatly, ashappened inthiscasestudy. Nevertheless, thefollowing results exclusively focus on those para-meters of the seed zone which were mainly affectedby the working system of openers and associatedpresswheelsratherthanbyothermechanicalcomponents.2.2. Field trialsTests were conducted over a period of 2 years(20022003) at a private farm in Teor (Udine, NEItaly: 458550N, 138100E, 8 m a.s.l.) in four fields withdiffering initial conditions (Table 1). The effects ofopeners were evaluated on some soil physicalT. Vamerali et al./Soil & Tillage Research 89 (2006) 196209199Fig. 2. Cerere multi-function trailed no-till air seeder with awide-sweep opener (top) and Max Emerge 2 no-till planter with double-disk opener(bottom).properties in the seed zone, surface soil morphologyand crop emergence and early root growth of maize(Zea mays, L.).In 2002, soils were both clay, with differingamountsofsoilorganiccarbon(SOC),1.45and2.27%in fields A and B, respectively. In 2003, the two fieldshad a different soil texture, with silty loam (field C)and silty-clay loam (field D), but with values of SOCwhich were more similar than in 2002. According tothe FAO classification, the soils of all fields wereclassified as Eutric fluvisols.Following suppression of cover crop with herbicidein March of both years, maize was sown on April 26,2002 and April 15, 2003, according to a theoreticalpopulation density of 8.2 and 7.7 plants m?2andwithin-row distances of 27.1 and 17.3 cm for WSOand DDO, respectively. The small discrepancy of seeddensity between openers was the minimum possible,compatible with the adjustment variations of theseeders. In any case, at least within the aim of thisresearch, the different plant spacing between openerscould not have affected the study parameters.In the test location, annual rainfall, as average ofperiod 19611990, is 1200 mm, 680 mm (57%) ofwhich falls between April and August. The annualaverage temperature is 12.9 8C, with a monthly peakin August (24 8C) and a minimum in December(1.5 8C). During the 2003 crop cycle (AprilAugust),the average temperature was higher and rainfall lowerthan the reference 30-year period values, whereas in2002, the opposite occurred for temperature butrainfall was very similar. In fact, total rainfall in 2002was 1410 mm, 46% (650 mm) of which fell during thecrop cycle, whereas in 2003, it was 966 mm, 37%(362 mm)ofwhichfellduringthecropcycle.Climaticdata, like rainfall and temperature, were provided bytheLocalRegionalAgencyforEnvironmentalProtection (ARPA) (Palmanova, Udine, Italy).Experimental observations on soil physical proper-ties and root density of maize were completed within25 days of sowing and no water was applied duringthis period. Data were measured after the completepassage of the seeder, so that soil parameters wereaffected by both opener and press wheels, allowingcomparisons between seeding units.The experiment involved one 20 m long ? 5 mwide plot per type of opener. According to proceduresof data analysis discussed by Gomez and Gomez(1984) for experiments in farmers fields, this trialmay be viewed as a comparison of two openers indifferent locations or environments, our fields beinglocated far away from each other. Plot size wasidentified as the field area large enough to accom-modate the experiment and with the least soilheterogeneity. Withinplots,soilsamplings andmeasurements were made before or after sowing witha different number of randomised replicates, depend-ingon the parameterinquestion.Statistical analysisofdata (ANOVA) was performed with Statgraphics 5.0Plus Software (Manugistics Inc., Rockville, MD,USA) and differences among means data wereevaluated by the LSD test at P ? 0.05.Parameters measured in the trial are reportedbelow.T. Vamerali et al./Soil & Tillage Research 89 (2006) 196209200Table 1Initial conditions of four fields in 2-year trial and soil characteristics in Teor (NE Italy)Year20022003Field AField BField CField DPrevious cropGlycine max Merr.Glycine max Merr.Sorghum vulgare L.Sorghum vulgare L.Cover crop (species of mixture)Avena sativa L.Avena sativa L.Triticum aestivum L.Triticum aestivum L.Vicia sativa L.Vicia sativa L.Vicia sativa L.Vicia sativa L.Vicia faba minor L.Secale cereale L.FAO soil classificationEutric fluvisolEutric fluvisolEutric fluvisolEutric fluvisolTexture (010 cm depth)ClayClaySilty loamSilty-clay loamSand (%)2119229Silt (%)21205355Clay (%)58612536Soil organic carbon (%)1.452.270.991.452.3. Sowing depthIn 2002 and 2003, respectively, at completeemergence, along four and two transects laid acrossfive sowing rows, one seedling per row therefore, atotal of 20 and 10 plants was completely extractedfrom the soil, allowing the length of the chlorophyll-free coleoptile to be measured. This measure wasconsidered as the depth of seed deposition; uniformityof sowing depth was calculated as the coefficient ofvariation of that depth, i.e., the ratio between standarddeviation and theoretical depth (3 cm). The higher thevalues of this parameter, the lower the uniformity.2.4. Plant emergenceTheemergenceratewascalculatedasthepercentage of emerging seedlings counted in a 3-m2sampling area distributed over five sowing rows (eightand five replicates in 2002 and 2003, respectively), atdifferent times after sowing. Counts were made 8, 10,12, 14, 21 and 25 days after sowing (DAS) in 2002 and6, 8, 14, 19 and 25 DAS in 2003. The percentage ofemergence was determined as the ratio betweennumber of emerging seedlings counted at each timewith respect to their final number (last observationdate). The Gompertz model (Goudriaan and van Laar,1994) turned out to be the most suitable for best-fittingthe time-course (x = time) of emergence (Y) asfollows:Y ce?e?bx?mCoefficients of regression c, b and m and the coeffi-cient of determination (R2) of each curve (treatment)are listed in Table 2. Graphically, the coefficientsindicate the maximum Y value (c), the x value at halfc (m) and the slope at flex (b).2.5. Seedbed roughnessSoil disturbance at the surface caused by theopeners was measured across sowing rows (fivereplicates in both years) in terms of seedbed rough-ness.The contour of the soil profile was marked withblack spray on an A4 sheet of white paper (21 cm ?29.7 cm), the longer side of which was set in the soiland supported by a zinc plate of the same size,orthogonally to the sowing row.According to the definition of Sandri et al. (1998),the roughness index was calculated as furrow standarddeviation (FRSD), i.e., the standard deviation ofheights (42 data) from the bottom of the sheet to thelower contour of the black paint measured at 0.5-cmintervals within 20-cm wide profiles centred aroundthe sowing row.2.6. Covering indexThe soil-covering index (CI) due to crop residueswas determined on digital pictures, taken by OlympusCamedia C2000Z camera, of fixed-size square areas(0.4 m ? 0.4 m) of the soil surface (four replicates inboth years) centred around the sowing row andrandomly set within plots. The same number ofreplicates was also considered before sowing. Residueincorporation (RI) was calculated as the differencebetween CI values before and after sowing.After transferring the images to a computer, avirtual 25-point regular square grid was overlaid onT. Vamerali et al./Soil & Tillage Research 89 (2006) 196209201Table 2Coefficients of regression (?S.D.) (Gompertz model) describing time-course of emergence in various treatmentsFieldOpenerCoefficientsR2cbmAWide-sweep96.2824 ? 2.93960.4236 ? 0.05968.7565 ? 0.22540.998ADouble-disk99.2545 ? 0.75700.5999 ? 0.03047.9177 ? 0.05620.999BWide-sweep97.1697 ? 3.23630.4957 ? 0.08718.3468 ? 0.24150.997BDouble-disk99.02 ? 0.67670.8779 ? 0.06487.5918 ? 0.05390.999CWide-sweep98.8516 ? 0.55341.2774 ? 0.60057.4987 ? 0.23630.999CDouble-disk97.8762 ? 1.73581.4639 ? 2.06257.3201 ? 0.95820.999DWide-sweep98.5250 ? 0.88901.3280 ? 0.88937.4308 ? 0.38200.999DDouble-disk98.7097 ? 0.52682.3322 ? 16.65157.0413 ? 6.76300.999the images, so that the presence or absence of residuesat each node could be counted manually. The CIwas calculated as the number of nodes intersectingresidues, according to the literature (Laflen et al.,1981; Cavalli and Sartori, 1988).2.7. Soil moisture and bulk densityImmediately after sowing (about 4 h later) 5-cmdeep undisturbed soil cores 8 cm in diameter werecollected, using a hand auger above the centre ofthe sowing row (five replicates). Gravimetric watercontent and bulk density were determined after oven-drying at 105 8C to constant weight. In 2003 weresamples also taken at six and eight DAS to determinesoil moisture only.2.8. Soil penetration resistanceIn both years, soil penetration resistance in furrowswas measured using a surface pocket penetrometer(Eijkelkamp, Glesbeek, NL) equipped with a flat-tipped measuring pin (6.4 mm diameter). Measureswere made every 1 cm over 5 cm deep profiles(vertical direction) at one side of the furrows for bothwide-sweep and disk openers, with three replicates(see Fig. 3). Profiles were taken at positi