用两种不同类型机头的联合收割机收割油菜时的种子损失外文文献翻译、中英文翻译
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Biosystems Engineering (2002) 81(3), 281286doi:10.1006/bioe.2001.0011, available online at onPM*Power and MachinerySeed Loss when Cutting a Standing Crop of Oilseed Rape with Two Types ofCombine Harvester HeaderR. N. Hobson; D. M. BruceBiomaterials Group, Silsoe Research Institute, Wrest Park, Silsoe, Beds. MK45 4HS, England; e-mail of corresponding author:norris.hobsonbbsrc.ac.uk(Received 8 July 2000, accepted in revised form 9 October 2001)Oilseed rape has the potential to expand as an industrial crop. However, as oilseed rape matures, seed lossoccurs by dehiscence of the seed from the pods prior to harvest and also as a result of crop disturbance bymachinery during harvest. Seed loss of 600 kgha?, 25% of the recorded yield, is not uncommon. This directlyincreases the price for industrial users and can also reduce oil purity because volunteer plants in subsequentoilseed rape crops may have a di!erent oil fatty acid prole. Oilseed rape plants also persist as weeds insubsequent crops. An experiment was carried out to identify the cause of, and quantify contributions to, seedloss from two di!erent designs of header tted to the combine harvester; a standard header and a header witha conveyor tted behind the cutterbar, claimed to assist crop #ow into the auger. Seed loss was measured usingtraysplaced in the ripening crop prior toharvest. Seedshed before harvest, 11 kgha?, was low as a result of therelatively settled weather conditions. There was a signicant di!erence between losses from the two types ofheader. The loss from each side knife was the same, but because of the di!ering header widths, translated intolosses of 18)4 and 34)6 kgha? for the conveyor-assisted and standard headers, respectively, showing theadvantage of using a wider header in reducing this loss. Excluding shedding loss and side knife losses, seed lossfrom the conveyor-assisted header was 59 kgh? against 104 kgh? with the standard header. Loss causedonly by the cutterbar of the conveyor-assisted header, 27 kgha?, was less than half that of the standard headercutterbar, showing the e!ectiveness of the combination of forward positioning of the cutterbar and conveyor-assistance. At 2001 costs, the conveyor-assisted header would recover its additional purchase price in ve yearsif used to harvest 171 ha of oilseed rape per year.? 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. Allrights reserved1. IntroductionOilseed rape (Brassica napus) is an important non-cereal, combinable break crop, the oil from which is usedmainly for food production (NIAB, 1992). Industrial ap-plications have also been developed for the oil; higherucic acid rape is grown for industrial lubricants (Cook-sley, 1993), rapeseed oil is convertible to bio-diesel (rapemethylester) (McDonnellet al., 1995) and forms the basisof a bio-degradable lubricant for underwater drilling(Coghlan, 1997). Several countries, in particular Franceand Austria, are actively promoting bio-diesel mainly asit is a renewable resource and also because it is seen asdelivering benets of lower emissions over standard die-sel, and therefore, nds favour in city centres and inenvironmentally sensitive areas such as the NorfolkBroads, England (Grimshaw, 1994). Oilseed rape isa plant that can be easily genetically engineered tochange the composition of the oil, so in the next fewyears, rapeseed could become an alternative and lessexpensive source of oil containing ricinoleic, petroselinic,stearic and lauric acids and jojoba wax, raw materials forplasticizers, pharmaceuticals, printing inks, cosmetics,detergents, lubricants and polymers (Murphy, 1993).The seed-bearing pods of this indeterminate plant be-come fragile and easily split open as the seed reachesmaturity, making plants with mature pods very suscep-tible to seed loss as a result of bad weather. As harvestingmust be done at seed maturity for maximum oil content,seed loss is also caused by disturbance of the plants1537-5110/02/$35.00/0281? 2002 Silsoe Research Institute. Published byElsevier Science Ltd. All rights reservedFig. 1. Schematic of conveyor-assisted header: (a), reel; (b),auger; (c), conveyor; (d) cutterbarduring harvesting operations (Ogilvy et al., 1992; Priceet al., 1996). In ideal conditions, seed loss can be as low as25% of yield, but a loss of 2025% has been recorded inweather conditions that were normal (Price et al., 1996)and loss can be as high as 50% in extreme cases (Mac-Leod, 1981). In autumn-sown varieties of oilseed rape,the extra plant height and longer period of seed ripeningmake harvesting generally more di$cult than witha spring sown crop. Price et al. (1996) found that, ina single crop of winter oilseed rape harvested at theoptimum time, 11% of the seed was lost compared withlessthan 3% in a spring-sowncrop, thoughthe harvestedyield of the winter rape, 2)76 tha?, still exceeded that ofthe spring rape, 2)57 tha?.There are two methods of harvest in common use. Inthe UK, about half of the crop is direct cut, i.e. thestanding plants are cut by combine in a single harvestoperation, usually after chemical desiccation, althoughsome of the crop is direct cut after a period of naturalripening typically several weeks longer than when desic-cation,is used. This avoids the cost of desiccation and thedisturbance to the crop caused by vehicles but leaves thecrop vulnerable to damage, particularly by wind or hail.The alternative to direct cutting is a two-stage harvest,involving swathing of the crop at an early stage of ripen-ing. According to Ogilvy (1989), swathing should takeplace when the seed colour in the bottom pods is darkbrown, middle pods redbrown with some green and thetop pods green and just turning brown, and the swathwill be ready for harvesting after a ripening and dryingperiod of 714 days.As seed loss tends to be higher during direct cutting ofoilseed rape than in the swathing method, several deviceshave been promoted which are claimed to reduce seedloss. One of these is a header that includes a conveyorbetween the cutterbar and auger (Fig. 1). This deviceassists the #ow of crop away from the cutterbar; so cutplants are not crushed by the auger until they are su$-ciently far behind the cutterbar for shed seed to be morelikely to fall on to the bed of the header, rather than belost. Also, there is likely to be less need to use the reel topull the crop onto the header in which case disturbanceto the top of uncut plants would be reduced. No reportsof the performance of this type of device were foundin the literature, so an experiment was carried out toquantify the loss from this type of header in autumn-sown oilseed rape and compare it with the loss froma standard header. Other approaches, not tested here,include reducing the auger speed and the use of anextended (static) table, i.e. a section is inserted into thebed of the header to move the cutterbar fartherin front ofthe auger.2. Materials and methods2.1. Harvesting equipmentEach of the two types of header was available on onlyone make of combine harvester, a conveyor-assisted(CA)header of 6)1 m width was tted to combine harvesterA and a standard header 3)6 m wide tted to combineharvester B. The standard header was typical of devicesin common use. Both headers had side knives; thestandard header had an electrically operated side knifetted retrospectively, whilst the CA header had mechan-ically driven side knives tted as original equipment.The main components of the CA header, shown in Fig. 1,are; (a), reel; (b), auger; (c), auger; (d), conveyor; (e),cutterbar.2.2. Experimental layoutThe work was carried out on a commercial farm inBedfordshire, UK, in a crop of winter oilseed rape, cul-tivar Capricorn. The crop was desiccated on 21 July 1994using Reglone applied with Dessicoat, and direct com-bine harvested on 6 August. There was a period of rela-tively good weather between desiccation and harvest,when the crop was most vulnerable to shedding,although there was a period of heavy rain 4 days prior toharvest. Seed loss caused by the operation to applydesiccant was not measured, but loss from the desiccatedcrop was measured. A uniform area of crop was chosenR. N. HOBSON; D. M. BRUCE282Fig. 2. Trayfor catching seed640 mmlong by 66 mm wide witha *V+ section, made ofsheet aluminium;the tray was inserted between,and held upright by, the rape stemsfor the experiment and its edges squared up by cutting.Working to a cut edge, a series of parallel runs wasmade through the crop. Alternate runs were madeby combine harvesters A and B, each tted with itsparticular header. Six runs were carried out by eachmachine.As counting seeds on, or collecting seeds from, the soilsurface is unreliable and very time consuming, a tech-nique developed at Silsoe Research Institute (Priceet al., 1996) was used. This technique employed traysplaced in the standing crop to catch samples of seedfalling from the crop itself and from the combineharvester. Trays (Fig. 2) with a narrow &V sectionmadeof sheet aluminium were slim enough to be insertedinto the limited space available between adjacent rapestems and, because of their steep sides, retained anyseed falling into them. Each tray was 640 mm long by66 mm wide with an included angle between the slopingsides of 403.The trays were placed in groups of 48, arrangedparallel to each other and to the direction of travel ofthe machine, with a gap of about 100mm between eachand approximately 1m into the crop from the endtowards which the machine was working. During eachrun, the machines harvested the crop in the normalmanner with gentle engagement of the reel with thecrop canopy. After the header but not the rest ofthe combine harvester had passed over the trays andnished cutting the crop strip, the combine harvesterwas halted to avoid the e%ux from the rear of thecombine harvester falling into the trays, and alsoto prevent its tyres crushing the trays. Once the combineharvester had withdrawn, the trays were extracted andtheir contents bagged for later drying so that the moist-ure content of the seed was approximately 8% wetbasis moisture, after which the seed was separated bysieving, and weighed.2.3. Shedding loss from the standing cropShedding loss occurs in the ripening crop prior toharvest, caused by any disturbance to the fragile pods asthey become ripe. This loss was assumed to be evenlydistributed.A week before harvest was due to commence, trayswere placed in the standing crop in the areas which hadbeen chosen as a suitable site for the harvest trials, takingcare not to disturb the crop. There had been no notice-able splitting of pods or shedding of seed prior to theinsertion of the trays. Immediately prior to harvest, thesetrays were removed from the crop and their contentscollected for later analysis.2.4. Header lossesThree positions for loss collection were chosen becausethey represented distinct sources of seed loss caused byan active contact between the crop and the componentsof the header.2.4.1. Side knife lossCrops of oilseed rape are usually highly branched andentangled. This makes it necessary during harvesting, todivide the crop at the side of the header by cutting ratherthan by a crop divider, used for cereals, that would tearthe crop and increase the loss. Side knives, in e!ectverticalcutterbars locatedat the front edge of each end ofthe header, cut through the standing crop. Owing to theirnecessarilyvigorous cutting action, someseed is shedandwhole pods and pieces of the pods are cut o!. The seedand pods fall onto the ground in a narrow band. Sideknife loss is, therefore, a concentrated loss and occurswith a spacing equal to the cutting width of the header.Previous experiments (Price et al., 1996) have shown that283SEED LOSS OF OILSEED RAPETable 1Analysis of seed loss dataLoss fromconveyor-assistedheader*Loss fromstandardheader*Diwerence inlossStandarderror ofdiwerenceProbabilityg6)337)010)681)370)631Side knifekgha?18)434)620)4-Cutterbarg0)901)941)040)3340)011kg ha?26)657)5Centreg per tray0)5340)7430)2090)1750)260kg ha?32)346)4*Six replicates.-Side knife loss from the standard header adjusted to correspond to the width of CA header.the loss from the side knife can be assumed to be uni-formly spread over a 300 mm width centred beneath theside knife. Although this loss is centred beneath the sideknife, it is measured by trays placed immediately outsidethe line of the side knife so that the trays do not collectany cutterbar loss. As only half of the loss distribution issampled, adjustments have to be made in calculating theloss. In addition, as the two headers had di!erent cuttingwidths, appropriate multipliers were used to express themean loss over the experimental plot. The conversionfactors calculated to convert seed mass collected in traysto mean loss for the plot are explained in Appendix A.2.4.2. Cutterbar lossAlthough the term cutterbar loss implies that thesource of this loss is solely the reciprocating cutterbar,which necessarily vibrates the stems as they are cut, lossmay also be caused by any contact of the combine har-vesters reel with pods, and by the auger behind thecutterbar tearing apart the entangled crop. Seed fallingonto the ground in front of the cutterbar was assumed tobe evenly distributed across its width.2.4.3. Centre lossThe crushing together at the centre of the header ofplants arriving from both ends causes some seed to bereleased, some of which is lost over the front of thecutterbar. This loss, termed centre loss, is superimposedupon cutterbar loss over the width of the centre opening,and can therefore be calculated by deducting the latter.Based on the previous measurements of its distribution(Price et al., 1996), the centre loss was sampled over thewidth of the centre opening of the machine and, toexpress it as a mean plot loss, multiplied by the ratio ofwidth of centre opening to header width (Appendix A). Inthe two headers used, the ratio of header width to widthof centre opening is very similar, 3)7:1 and 3)8:1 for theCA and standard headers, respectively.3. ResultsThe harvested yield from the plot as a whole was 2)2tha?. Compared with harvested yield, shedding loss at11)0 kgha? (0)5% of harvested yield), was relativelyunimportant in this particular crop, helped by settledweather before harvest.To compare the cutterbar and the side knife lossesbetween machines, data were analysed at the level ofmass of seed collected in the trays because this avoidedthe use of any scaling factors for header width, etc. Toobtain the centre losses, the cutterbar losses had to besubtracted, but the number of trays used to measurecentre loss was not the same as the number used forcutterbar loss, so the data in this case were compared onthe basis of mass/tray. Table 1 shows the data and theresults of the analysis of variance. Figure 3 shows thelosses in kg ha? calculated using scaling detailed inAppendix A.Adding all the losses including the shedding loss to-gether, the total for the CA header was 88)3 kgha? andfor the standard header was 149)5 kgha?. However,these values are not a fair basis for comparison of theheaders because the side knife loss is, in principle, inde-pendent of the cutting width of the header. This is con-rmed by analysis in Table 1 of the mass of seed collectedin the four trays beneath each side knife, 6)33 g from theCA header and 7)01 g from the standard one, which werenot signicantly di!erent (probability, P0)631). Whenexpressed on a plot basis, side knife losses from the CAheader and standard header were 18)4 and 34)6 kgha?respectively, which highlight the benet of using a widerheader in reducing the loss from this source.The cutterbar loss from the CA header was signi-cantly less (P0)011) than the loss from the standardheader, as shown in Table 1. The conveyor-assistedheaderreduced the loss from the cutterbarto 46% of thatfrom the cutterbar of the standard header. The reducedR. N. HOBSON; D. M. BRUCE284020406080100120140160 SheddingConveyor assistedStandardSeed loss, kg ha_1Fig. 3. Measured seed loss shed from standing crop, and causedby three elements of two headers; losses are not adjusted forheader width; six replicate observations were made; bars, $1standard error of the mean;, shedding losses;, side knifelosses;, cutterbar losses;, centre losses;, total lossesloss from the CA header is likely to be a result of (a)increased distance of the cutterbar from the auger, whichallows more loose seed to be collected rather than fallingon the ground, (b) more e!ective transport of crop intothe auger by the conveyor, allowing room for the nextcrop to be harvested and, (c) less need for the reel to beused to pull the cut crop onto the header, becausethe crop is actively fed into the auger, thereby reducingthe damage from contact with the reel. While the cropharvested here was relatively short, it was well suited todirect cutting. The di!erence in cutterbar losses may beexpected to increase in taller, more tangled crops, whichthe CA header would be able to harvest with less need forcontact with the reel.Although the measured seed loss from the centre sec-tion of the CA header was lower than that from thestandard one, the di!erence was not great enough to besignicant (P0)26). The ratio of header width to widthof centre opening was very similar for the two headers sothe nominal degree of crushing of the cut crop arriving atthe centre was similar for each. Increasing the distance ofthe cutterbar from the auger would be expected to reduceseed loss from the centre section, but the present resultsdo not demonstrate this. For the CA header, the centreloss was 21% higher than the cutterbar loss, which sug-gests that further study of the machine/crop interactionin the centre region would be benecial.Excluding shedding and side knife losses, the CAheader lost 58)9 kgha? compared with 103)9 kgha?for the standard header, a saving of 45 kgha?.Further work is needed (a) to elucidate how the con-veyor-assisted header achieves lower seed loss so that itsaction could be further improved; (b) to compare theperformance of the conveyor-assisted device with that ofthe simpler device of an extended table and to investigatewhether slower auger speeds reduce seed loss; (c) to studythe causes of centre loss; (d) to evaluate header perfor-mance in a range of oilseed rape crops, because cropsvary widely in susceptibility to losses depending on stageand evenness of ripeness, canopy structure, cultivar andweather preceding harvest; and (e) to investigate andquantify the benets from using a CA in the mainstreamcereal crops and other alternative crops.4. Economic evaluationAlthough the crop used for the experiment was parti-cularly suitable for direct cutting, in that the overall losswas low compared with previously measured losses, useof a header with the CA design rather than the standarddesign of header saved 45 kgha? of seed, worthC5)85 ha? to the producer at a market price of seed ofC130 t? (March 2001). The di!erence in list price fora CA header of width 6)10 m compared with a standardheader of the same width from the same manufacturer isC5680,or around C5000 after discount.Assuming that theextra cost of the header is depreciated over 5 years andthat the savings found in this crop were consistentlyachieved, then the header would have to harvest 171 hay?of oilseed rape to justify the increased purchaseprice.The payback would be improved by any saving in loss onother combinable crops, or reduction in spraying costs asa result of fewer volunteer rape plants in subsequentcrops.5. ConclusionsThe 6)1 m wide conveyor-assisted (CA) header produ-ced signicantly lower loss than the 3)6 m wide standardheader; total header loss from the CA header of88)3 kgha?(4)0%ofharvestedseedyieldof2200 kgha?) was 59% of that from the standard headerat 149)5 kgha? (6)8%). Eliminating side knife loss(which was the same for each side knife and only di!eredbetween headers because the headers were of di!erentwidths) and pre-harvest shedding loss, the loss from theCA header was 59 kgha?, 57% of the 104 kgha? fromthe standard header. Cutterbar loss was reduced from58 kgha? for the standard to 27 kgha? for the CAheader. Centre loss was not signicantly a!ected. Shed-ding loss at 11 kgha?, 0)5% of the harvested yield wassmall in comparison to the overall loss caused by har-vesting. The highest component of the loss from the CAheader was the centre loss. Assuming that a 6)1 m CAheader was operated in oilseed rape alone, it would need285SEED LOSS OF OILSEED RAPEto harvest more than 171 hayr? over 5 years to recoupits extra initial cost, compared with a standard
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