手推式電動小型免耕播種機設(shè)計【18張CAD圖紙+PDF圖】

喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請放心下載，，有疑問咨詢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，，請放心下載，，有疑問咨詢QQ:414951605或者1304139763 ======================== 任務書 論文(設(shè)計)題目：手推式免耕播種機三維設(shè)計 工作日期：2017年12月18日 ~ 2018年05月25日 1.選題依據(jù): 播種機是現(xiàn)代農(nóng)業(yè)必備的設(shè)備之一，也是農(nóng)業(yè)現(xiàn)代化的重要標志。除此之外，免耕播種技術(shù)是一種保護性耕作技術(shù)，能保護農(nóng)田、減少農(nóng)田揚沙、減少土壤風蝕和水蝕。手推式免耕播種機，主要適應面積狹小、山地、坡地等不適合大中型播種機工作的地方 。它可以大大提高播種效率，降低勞動強度，制造成本低，結(jié)構(gòu)簡單，操作方便，由一人就可以提供動力，播種精準，也能節(jié)約大量的種子。同時，維修更換配件也簡單方便 。 2.論文要求(設(shè)計參數(shù)): 1.總體結(jié)構(gòu)設(shè)計，要求該機器能夠一人獨立操作使用。至少兩種設(shè)計方案比較優(yōu)選 ，并驗證播種機的穩(wěn)定性。 2.各子結(jié)構(gòu)設(shè)計，完成開溝、排種、施肥、覆土、壓土等各項功能。 3.鏈傳動系統(tǒng)設(shè)計，完成鏈輪的設(shè)計、主動軸、被動軸的設(shè)計計算和校核。 4.機架部分的設(shè)計，包括機架、地輪、種箱、肥箱的設(shè)計。 5.動力系統(tǒng)設(shè)計 6.繪制各部件的工程圖紙，圖量不小于三張A0，必須有一個其中部件的3D圖。撰寫設(shè)計說明書，字數(shù)不少于6000字。 產(chǎn)品技術(shù)參數(shù)要求 外形大?。╟m）：100×60×120（最大） 播種行數(shù)：兩行 行距（mm）：300~500 株距（mm）：200~400 播種深度（mm）：30~60 3.個人工作重點: 1.鏈傳動系統(tǒng)的設(shè)計計算及校核。 2.鏈輪的設(shè)計，可調(diào)株距備用鏈輪設(shè)計。 3.主、從動軸的設(shè)計計算及校核。 4.運用三維繪圖軟件繪制整機或者某個部件的裝配圖，并做爆炸視圖和動畫演示。 4.時間安排及應完成的工作: 第1周：了解題目研究的主要內(nèi)容和理論意義及應用價值，查閱有關(guān)文獻。 第2周：查閱文獻、閱讀文獻，了解研究的內(nèi)容及實現(xiàn)的技術(shù)路線 第3周：撰寫文獻綜述并完成開題報告 第4周：修改開題報告及文獻綜述準備開題答辯。 第5周：總體結(jié)構(gòu)的設(shè)計，各子機構(gòu)的功能總體設(shè)計，繪制二維總裝配圖草圖 第6周：鏈傳動系統(tǒng)設(shè)計，完成鏈輪的設(shè)計、主動軸、被動軸的設(shè)計計算和校核。 第7周：鏈輪的設(shè)計，可調(diào)株距備用鏈輪設(shè)計。 第8周：動力系統(tǒng)設(shè)計。主動軸、從動軸的設(shè)計計算及校核。 第9周：排種器及排肥器的機構(gòu)設(shè)計及尺寸計算 第10周：機架部分的設(shè)計，包括機架、地輪、種箱、肥箱的設(shè)計，繪制二維工程圖草圖 。 第11周：修改并完成部件二維工程圖 第12周：繪制其中一個部件的三維裝配圖，并做爆炸視圖和動畫演示。 第13周：撰寫設(shè)計說明書 第14周：提交論文、圖紙、查重報告，準備答辯 5.應閱讀的基本文獻: [1]濮良貴，陳國定，吳立言主編.《機械設(shè)計（第九版）》[M].北京：高等教育出版社 ，2013.5 [2]耿端陽主編.《新編農(nóng)業(yè)機械學》 [M].北京：國防工業(yè)出版社，2011.12 [3]聞邦椿主編.《現(xiàn)代機械設(shè)計實用手冊》[M].北京：機械工業(yè)出版社 [4]孫桓，陳作模，葛文杰主編.《機械原理（第八版）》[M]，高等教育出版社，2013.4 [5]佘大慶.國內(nèi)外免耕播種機研究概況[J].農(nóng)業(yè)工程，2016 [6]王玉華.可調(diào)式免耕播種施肥機的設(shè)計研究[J].農(nóng)業(yè)科技與裝備，2013 [7]畢曉偉.免耕播種機的現(xiàn)狀與發(fā)展趨勢[J].內(nèi)蒙古民族大學學報（自然科學版），2013 [8]白曉虎.免耕播種機關(guān)鍵部件及其參數(shù)化設(shè)計方法研究[D].沈陽農(nóng)業(yè)大學博士學位論文 ，2012 [9]張旭，劉飛，董帥，等.免耕播種機排種裝置振動試驗研究[J].中國農(nóng)機化學報，2015 [10] 張守德，杜健民，郝飛，等.2BQM-6型免耕播種機結(jié)構(gòu)設(shè)計及開溝器的力學分析[J].農(nóng)機化研究，2016 [11]楊慧.小麥免耕播種機的研究[D].安徽農(nóng)業(yè)大學碩士學位論文，2014 [12]高娜娜，張東興，楊麗，等.玉米免耕播種機滾筒式防堵機構(gòu)的設(shè)計與試驗[J].農(nóng)業(yè)工程 學 報 ，2012 [13]申冰冰主編.《實用機構(gòu)圖冊（第二版）》[M].北京:機械工業(yè)出版社，2013 指導教師簽字： XX 教研室主任意見： 同意 簽字：XX 2017年12月14日 教學指導分委會意見： 同意 簽字：XX 2017年12月15日 學院公章 進度檢查表 第 -4 周 工作進展情況 確認選題之后，搜集了相關(guān)的一些期刊、論文等資料，閱讀整理之后撰寫了文獻綜述，同時查找了相關(guān)的外文文獻并做了閱讀翻譯。 2018年01月11日 指導教師意見 講解設(shè)計題目要求和理論意義及應用價值。講解開題報告的內(nèi)容及寫作方法，講解文獻資料的查閱及文獻綜述的寫作要求。該生能充分領(lǐng)會選題的內(nèi)容及意義。 指導教師(簽字)：XX 2018年01月11日 第 -1 周 工作進展情況 修改整理文獻綜述，了解國內(nèi)外免耕式手推播種機的發(fā)展歷程以及現(xiàn)狀 ，并對其整理，完成開題報告的相關(guān)工作。同時對整個課題所需的工作做出了詳細計劃。 2018年01月11日 指導教師意見 開題報告中的工作時間安排合理，技術(shù)路線規(guī)劃切實可行。文獻資料查閱比較充，文獻綜述格式正確，內(nèi)容詳實。 該生能較好地完成開題報告，及開題答辯。同意開題。 指導教師(簽字)：XX 2018年01月11日 第 5 周 工作進展情況 進行子結(jié)構(gòu)的功能設(shè)計，并繪制二維草圖，對各子結(jié)構(gòu)進行功能分析 ，確定各部件在總裝配中的位置并完成二維總裝草圖。 2018年04月06日 指導教師意見 工作進度按計劃進行，各子部分設(shè)計合理可信。設(shè)計計算需要進一步校核及更改設(shè)計圖紙。二維草圖需要標注全技術(shù)要求。三維部分的裝配關(guān)系需要進一步檢驗裝配干涉問題，及時修改。 指導教師(簽字)：XX 2018年04月07日 第 10 周 工作進展情況 完成各子結(jié)構(gòu)的尺寸計算及校核，繪制各結(jié)構(gòu)三維圖并完成總裝配以及實現(xiàn)部分關(guān)鍵部件的爆炸效果，整理計算過程并完成設(shè)計說明書。 2018年05月12日 指導教師意見 總體設(shè)計進度按要求完成。三維裝配中，各子結(jié)構(gòu)的鏈接裝配需要核實 ，部分高級裝配，要做干涉檢查。三維圖生成二維圖紙過程中，一些不合理的尺寸需要刪掉和修改。二維圖紙需要標注全技術(shù)要求。三維爆炸視圖基本合理。設(shè)計說明書格式需要進一步修改。 指導教師(簽字)：XX 2018年05月12日 過程管理評價表 評價內(nèi)容 具體要求 總分 評分 工作態(tài)度 態(tài)度認真，刻苦努力，作風嚴謹 3 3 遵守紀律 自覺遵守學校有關(guān)規(guī)定，主動聯(lián)系指導教師,接受指導 3 3 開題報告 內(nèi)容詳實，符合規(guī)范要求 5 4 任務完成 按時、圓滿完成各項工作任務 4 4 過程管理評分合計 14 過程管 理評語 該同學工作態(tài)度認真，學習態(tài)度端正，工作作風較為嚴謹，能夠聯(lián)系老師，虛心接受指導。 該生能自覺遵守校規(guī)校紀，在畢業(yè)設(shè)計階段能夠較為專心做設(shè)計，基本能按擬定的進度計劃開展畢業(yè)設(shè)計工作。 該生有一定的文獻資料檢索能力，占有資料較為全面，開題報告的撰寫內(nèi)容較為詳實，格式基本符規(guī)范要求，文獻綜述較為全面 ，外文翻譯基本正確可信。 中期檢查能夠按時達到計劃進度的設(shè)計任務。整個畢業(yè)設(shè)計全程能夠基本按照擬定的計劃完成各階段的任務。最后的論文設(shè)計圖紙等按時提交。 指導教師簽字:XX 日期:2018-05-23 指導教師評價表 評價內(nèi)容 具體要求 總分 評分 選題質(zhì)量 符合培養(yǎng)目標要求,有一定的研究價值和實踐意義,有一定的開拓性、創(chuàng)新性,深度、難度適宜,工作量飽滿 5 5 能力水平 有較強的綜合運用知識能力、科研方法運用能力、中文表達與外語能力、文獻資料檢索能力、計算機應用能力 5 4 完成質(zhì)量 文題相符,概念準確,分析、論證、計算、設(shè)計、實驗等正確合理,結(jié)論明確；論文結(jié)構(gòu)、撰寫格式、圖表等符合基本規(guī) 10 7 指導教師評分合計 16 指導教 師評語 設(shè)計題目來源于農(nóng)業(yè)機械化半機械化生產(chǎn)實踐，有一定的研究價值和和實際意義，符合機械設(shè)計制造及其自動化專業(yè)培養(yǎng)目標要求，該題目深度、難度適宜，工作量飽滿，尤其是三維繪圖工作量較大。 該同學有一定的綜合運用所學專業(yè)知識的能力，科研方法運用能力較好，中英文表達能力尚好，有較好的文獻資料檢索能力，計算機應用能力熟練。 該設(shè)計文題相符，分析、設(shè)計、計算基本正確，結(jié)論可信。說明書結(jié)構(gòu)、圖、表等基本符合規(guī)范要求。 同意參加答辯。 指導教師簽字:XX 日期:2018-05-23 評閱人評價表 評價內(nèi)容 具體要求 總分 評分 選題質(zhì)量 符合培養(yǎng)目標要求,有一定的研究價值和實踐意義,有一定的 開拓性、創(chuàng)新性,深度、難度適宜,工作量飽滿 5 4 能力水平 有較強的綜合運用知識能力、科研方法運用能力、中文表 達與外語能力、文獻資料檢索能力、計算機應用能力 5 4 完成質(zhì)量 文題相符,概念準確,分析、論證、計算、設(shè)計、實驗等正確 合理,結(jié)論明確；論文結(jié)構(gòu)、撰寫格式、圖表等符合基本規(guī) 10 7 評閱人評分合計 15 評閱人 評語 溫室大棚的發(fā)展以及環(huán)保發(fā)展意識的日益增強，小型機的需求就顯得更為重要。以手推式免耕播種機的設(shè)計為題，符合本專業(yè)培養(yǎng)目標的要求，具有一定的實際應用價值，難度和工作量適中。吳博同學完成了手推式免耕播種機各組成結(jié)構(gòu)的設(shè)計與計算，繪制了相應的機械結(jié)構(gòu)圖。設(shè)計說明書內(nèi)容較為完整、層次基本清晰、格式符合基本規(guī)范、公式引用及計算合理，繪制的工程圖樣符合基本標準要求，但工程圖樣的尺寸標注、細節(jié)表達等尚有欠缺。提交的設(shè)計資料及過程表現(xiàn)反映出該生具備基本的知識綜合應用能力、文字表達能力和使用工程軟件進行設(shè)計的能力。 評閱人簽字：XX 評閱人工作單位：XX日期：null 答辯委員會評價表 評價內(nèi)容 具體要求 總分 評分 自述總結(jié) 思路清晰,語言表達準確,概念清楚,論點正確,分析歸納合理 10 7 答辯過程 能夠正確回答所提出的問題,基本概念清楚,有理論根據(jù) 10 7 選題質(zhì)量 符合培養(yǎng)目標要求,有一定的研究價值和實踐意義,有一定的 開拓性、創(chuàng)新性,深度、難度適宜,工作量飽滿 5 5 完成質(zhì)量 文題相符,概念準確,分析、論證、計算、設(shè)計、實驗等正確 合理,結(jié)論明確；論文結(jié)構(gòu)、撰寫格式、圖表等符合基本規(guī) 10 8 能力水平 有較強的綜合運用知識能力、科研方法運用能力、中文表 達與外語應用能力、文獻資料檢索能力、計算機應用能力 10 7 答辯委員會評分合計 34 答辯委員會評語 吳博同學在畢業(yè)設(shè)計工作期間，工作努力，態(tài)度比較認真，能遵守各項紀律，表現(xiàn)一般。 能按時、全面、獨立地完成與畢業(yè)設(shè)計有關(guān)的各環(huán)節(jié)工作，具有一定的綜合分析問題和解決問題的能力。 論文立論正確，理論分析無原則性的錯誤，解決問題方案比較實用，結(jié)論正確。 論文使用的概念正確，語句通順，條理比較清楚。 論文中使用的圖表，設(shè)計中的圖紙在書寫和制作時，能夠執(zhí)行國家相關(guān)標準，基本規(guī)范。 能夠獨立查閱文獻，外語應用能力一般，原始數(shù)據(jù)搜集得當，實驗或計算結(jié)論準確可靠。 答辯過程中，能夠簡明地闡述論文的主要內(nèi)容，回答問題基本正確，但缺乏深入地分析。 答辯成績： 34 答辯委員會主任： XX 2018年05月30日 成績評定 項目分類 成績評定 過程管理評分 14 指導教師評分 16 評閱人評分 15 答辯委員會評分 34 總分 79 成績等級 C 成績等級按“A、B、C、D、F”記載 成績審核人簽章： XX 審核人簽章： XX 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