(1.4)--Multiple Cropping system耕作制度耕作学.PDF

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1、Chapter VMultiple Cropping Systems:A Basis for Developing anAlternative AgricultureDr.Stephen R.GliessmanEnvironmental StudiesUniversity of CaliforniaContentsPageAbstract.69Introduction.69Concepts and Definitions.70The Basis of Multiple Cropping.71Yield Advantages of Crop Mixtures.71General Resource

2、 Use.73Specific Resource Use,Conservation,and Management.75Agroforestry:A Multiple Cropping System.79Socioeconomic Implications of Multiple Cropping Systems:Perspectives for the Future.80References.82List of TablesTable No.Pagel.Definitions of the Principle Multiple Cropping Patterns.712.Related Ter

3、minology Used in Multiple Cropping Systems.713.Biological and Physical Factors:The Advantages and Disadvantages of MultipleCropping Systems Compared to Sole-Cropping or Monoculture Systems.724.Social and Economic Factors:The Advantages and Disadvantages of MultipleCropping Systems Compared to Sole-C

4、ropping or Monoculture Systems.73S.Yields of Corn,Beans,and Squash Planted in Polyculture as Compared to Lowand High Densities of Each Crop in Monoculture.746.Effects of Mixed and Row Intercropping on Yields and Nutrient Uptake ofCorn and Pigeon Peas in St.Augustine,Trinidad,Expressed as Relative Yi

5、eldTotals.767.Biomass Distribution of Dry Matter in a Corn/Bean Polyculture as Compared toa Corn Monoculture,in Tacotalpa,Tabasco,Mexico.768.Classification and Examples of Agroforestry Technologies.80FigureFigure No.Pagel.Distribution of the Relative Yield Totals of Mixtures Based on 572 PublishedEx

6、periments.72Chapter VMultiple Cropping Systems:A Basis for Developing anAlternative AgricultureThis paper presents a general discussion ofthe concept of multiple cropping,including adescription of the different types of systems,and the advantages and disadvantages of theirwidespread use,both biologi

7、cal and socio-economical.These systems are designed to in-tensify agricultural production both in termsof yields per unit area and through the moreefficient use of space and time.Examples of yield increases with multiplecropping systems are expressed in terms ofRelative Yield Totals(RYT)or Land Equi

8、valentUse(LER)where the production per unit areawith the multiple crops is greater than the sumof equivalent areas planted to monoculture.This increase in production is explained byhigher overall efficiency of resource use.Specific examples of the effects of multiplecropping systems on resource use,

9、conserva-tion,and management are discussed,Variablesconsidered include microclimate,light,soil,water,pests,diseases,weeds,crop interac-tions,space,and time.The special case ofagroforestry,which combines trees with cropsand grasses,is discussed.In conclusion,the socioeconomic implica-tions,both advan

10、tageous and disadvantageous,are discussed.Also,the great potential formultiple cropping systems in agriculture in theUnited States is presented.Research needs tobe directed to test these alternatives.Multiple cropping is not a new form of agri-cultural technology,but instead is an ancientmeans of in

11、tensive farming.Multiple croppinghas been practiced in many parts of the worldas a way to maximize land productivity in aspecific area in a growing season.Generally,the practice of planting two or more crops onthe same field is more common in tropical re-gions where more rainfall,higher tempera-ture

12、s,and longer growing seasons are morefavorable for continual crop production.Aspopulation has increased,increasing the needfor agricultural production,the use of multi-cropping systems is more prevalent.Thoughthe history of multiple cropping is old,the con-cept has received very little attention fro

13、m agri-cultural scientists,and what limited interest ex-ists has come about very recently.Why was this interest increased so dramat-ically in such a short time?Food shortages inmany parts of the world,as well as the threatof insufficient supplies in the near future,con-tinues to stimulate more inten

14、sive agriculturalinvestigation in a search for more productivealternatives.As a consequence,it appears that6970we are about to embark on a new phase of agri-cultural research.Exactly what form it will takeis still not known,but the reasons for this newapproach are rapidly becoming apparent.First,we

15、have begun to observe a leveling offin yield increases brought about by the typesof genetic manipulation that gave us such rapidand impressive yield increases during the“Green Revolution.”It is as if we have reacheda“yield plateau”with the current lines of re-search and crop selections.Large-scale u

16、se ofsingle varieties(e.g.,some of the InternationalRice Research Institute(IRRI)varieties of rice),with broad adaptability,produced major break-throughs in yields.But it appears that these va-rieties have almost reached their maximumyield potentials.In many areas with specificsoil and climatic cond

17、itions,they have not per-formed as well as hoped,especially on landmore difficult to mechanize or irrigate.Thuswe must begin to look for varieties with morespecific adaptability and selected for specificenvironments,or else consider alternativecropping systems.best agricultural landsareas with good

18、soiland easy water control.Future increases inproduction,therefore,will demand a new andinnovative way of managing these highly pro-ductive lands,as well as looking for methodsto make marginal lands increasingly produc-tive.Only 20 percent of Asia rice land,for ex-ample,is irrigated,and the new high

19、 yieldingrice varieties(which also require high levels offertilizers,water use,and pest control)have notpenetrated much beyond this boundary(16).The third factor is the oil crisis.Oil pricescontinue to soar,and with them,the cost offer-tilizers,pesticides,and fuel needed to build andrun farm equipme

20、nt and move irrigation water.Costs continue to mount for those inputs mostresponsible for achieving the dramatic yield in-creases of the“Green Revolution.”We arefaced with the necessity of having to considerother alternatives that might allow us to sub-stitute innovative biological or agronomic prac

21、-tices and varieties for these high cost inputs.Multiple cropping offers one of the most im-portant and promising of these alternatives.Second,most of the dramatic yield increasesduring the past few decades have been on theCONCEPTS AND DEFINITIONSMultiple cropping systems use managementpractices whe

22、re the total crop production froma single piece of land is achieved by growingsingle crops in close sequence,growing sev-eral crops simultaneously,or combining singleand mixed crops in some sequence.The mostimportant aspect of multiple cropping is theintensification of crop production into addi-tion

23、al dimensions.Multiple cropping includesthe dimensions of time and space;for exam-ple,when two crops share the same space atthe same time.A classification of types of multiple croppingsystems is presented in table 1.Note thatspecial emphasis is placed on the distinctionbetween intercropping,where tw

24、o or morecrops are grown at the same time,and sequen-tial cropping,where two or more crops aregrown on the same piece of land,but one fol-lowing the other.Some additional terms used in multiple crop-ping are presented in table 2.Agroforestry,asa particular type of intercropping system,willbe discuss

25、ed in some detail.Also,“mixed crop-ping,“polyculture,”and“multiple cropping”will be used interchangeably in this review.Bycombining different aspects of simultaneousand sequential cropping systems,it is possibleto visualize a truly complex pattern of differentmultiple cropping systems.This classific

26、ationwill be used throughout the following discus-sion,based on a symposium sponsored by theAmerican Society of Agronomy,in support ofthe need to standardize terminology(34).71Table 1.Definitions of the Principal MultipleCropping PatternsG Multiple Cropping:The intensification of cropping in timeand

27、 space dimensions.Growing two or more crops on thesame field in a year.c Intercropping:Growing two or more crops simultaneouslyon the same field per year.Crop intensification is in bothtime and space dimensions.There is intercrop competi-tion during all or part of crop growth.Farmers manage morethan

28、 one crop at a time in the same field.Mixed intercropping:Growing two or more crops simul-taneously with no distinct row arrangement.Row intercropping:growing two or more cropssimultaneously with one or more crops planted in rows.Strip intercropping:Growing two or more crops simul-taneously in diffe

29、rent strips wide enough to permit in-dependent cultivation but narrow enough for the cropsto interact agronomically.Relay intercropping:Growing two or more crops simul-taneously during part of each ones life cycle.A secondcrop is planted after the first crop has reached itsreproductive stage of grow

30、th,but before it is ready forharvest.G Sequential Cropping:Growing two or more crops i n se-quence on the same field per year.The succeeding cropis planted after the preceding one has been harvested.Cropintensification is only in the time dimension.There is nointercrop competition.Farmers manage onl

31、y one crop ata time.Double cropping:Growing two crops a year in sequence.Triple cropping:Growing three crops a year in sequence.Quadruple cropping:Growing four crops a year in se-quence.Ratoon cropping:Cultivating crop regrowth after harvest,although not necessarily for grain.SOURCE Andrews and Kass

32、am,1976(5)Table 2.Related Terminology Used in MultipleCropping SystemsSingle Stands:The growing of one crop variety alone in purestands at normal density.Synonymous with“solid plant-ing,“sole cropping.”Opposite of(multiple cropping.”Monoculture:The repetitive growing of the same crop on thesame land

33、.Rotation:The repetitive growing of two or more sole cropsor multiple cropping combinations on the same field.Cropping Pattern:The yearly sequence and spatial arrange-ment of crops,or of crops and fallow on a given area.Cropping System:The cropping patterns used on a farm andtheir interactions with

34、farm resources,other farm enter-prises,and available technology that determine theirmakeup.Mixed Farming:Cropping systems that involve the raisingof crops and animals.Cropping Index:The number of crops grown per annum ona given area of land multiplied by 100.Relative Yield Total(RYT):The sum of the

35、intercropped yieldsdivided by yields of sole crops.The same concept as landequivalent ratios.“Yield”can be measured as dry matterproduction,grain yield,nutrient uptake,energy,or proteinproduction,as well as by market value of the crops.Land Equivalent Ratios(LER):The ratio of the area neededunder so

36、le cropping to the one under intercropping to giveequal amounts of yield at the same management level.The LER is the sum of the fractions of the yields of theintercrops relative to their sole-crop yields.It is equivalentto RYT,expressed in commercial yields.Income Equivalent Ratio(IER):The ratio of

37、the area neededunder sole cropping to produce the same gross incomeas is obtained from 1 ha of intercropping at the samemanagement level.The IER is the conversion of the LERinto economic terms.SOURCE Sanchez,1976(39)THE BASIS OF MULTIPLE CROPPINGYield Advantages of Crop MixturesIn areas of the world

38、 where multiple crop-ping is a common aspect of agroecosystemmanagement,productivity generally is morestable and constant in the long term(24,45).Farmers often are able to achieve a combinedproduction per unit area greater with a cropmixture than with an equal area divided amongseparate crop units.I

39、n such cases the RelativeYield Total(RYT)is greater than 1.0.It maybe that each crop in the mixture yields slightlyless than the monoculture,but the combinedyield of the mixture on less total land area isthe important aspect.In one study(43),the results of 572 com-parisons of crop mixtures demonstra

40、ted thatthe majority(66 percent)had RYTs close to 1.0,indicating no distinct advantage to the mixture(fig.1).On the other hand,20 percent of themixtures had RYTs greater than 1.0,rangingup to 1.7,indicating advantages to the mix-tures.Only 14 percent had less than 1.0,in-dicating distinct disadvanta

41、ges.It must beremembered that most of the cases studied72Figure 1.Distribution of the Relative Yield Totals ofMixtures Based on 572 Published Experiments0.5 0.7 0.9 1.1 1.3 1.5 1.7Relative yield totals(RYT)SOURCE Trenbath,1974(43)were experimental planting and not actualmultiple cropping systems.Far

42、mers wouldtend to choose the systems that yield more,aswe have observed in traditional agroecosys-tems in the lowland tropical areas of southeast-ern Mexico(24,25).The fact that advantageous mixtures do ex-ist demonstrate the need for detailed researchto take proper advantage of such systems.Butfor

43、such systems to be considered as actualalternatives we need to understand thoroughlythe biological and agronomic basis responsi-ble for the observed response,as well as theadvantages and disadvantages to their use.Before beginning a discussion of each aspect,a basic outline of such characteristics i

44、s pre-sented,separated broadly into biological andphysical aspects(table 3)and socioeconomicaspects(table 4).In many cases it is understoodthat there may be overlap between the twoclassifications,yet it is hoped that in the courseof the following discussion that such aspectswill be clarified.Table 3

45、.Biological and Physical Factors:The Advantages and Disadvantages of MultipleCropping Systems Compared to Sole-Cropping orMonoculture Systems(priority is not established)Advantages-1.It is possible to obtain a better use of vertical space and2.3.4.5.6.7.8.9.10.11.12.13.14.15.16.time”,imitating natur

46、al ecological patterns in regards tostructure of the system,and permitting efficient captureof solar energy and nutrients.Greater amounts of biomass(organic matter)can bereturned to the system,sometimes even of better quality.There exists a more efficient circulation of nutrients,in-cluding their“pu

47、mping”from the deeper soil profileswhen deeper rooted shrubs or trees are included.The damaging effects of wind sometimes can bereduced.Systems can be designed that are appropriate for(butnot restricted to)marginal areas because multiple crop-ping systems can better take advantage of variable soil,t

48、opography,and steeper slopes.Multiple cropping systems are less subject to variabili-ty in climatic conditions,especially extremes of rainfall,temperature,or wind.Reduction of water evaporation from the soil surface.Increased microbial activity in the soil.Avoidance or reduction of surface erosion.F

49、ertilizer use can be more efficient because of the morediverse and deeper root structure in the system.Improved soil structure,avoiding the formation of a“hardpan”and promoting better aeration and filtration.Legumes(as well as a few other plant families)are ableto fix and incorporate nitrogen into t

50、he system.Heavier mulch cover aids in weed control.Better opportunities for biological control of insects anddiseases.Crop mixtures better permit the functioning of complexmutualisms and beneficial interactions between or-ganisms.Better use of time,with more crops per unit time in thesame area.Disad