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Chapter 15

Future Perspectives of Multiple Cropping

Charles A. Francis

There is an increasing recognition by scientists and agricultural aaministrators of the current and potential future importance of multiple cropping systems. This importance was discussed in the introductory chapter. In a conference inaugu­ ratiot, the Minister of Agriculture of Tanzania, Hon. John S. Malacela (1982) observed that.

The fact that mixed cropping is the way of life for the sbsistence farmer in the tropits underscores the reasons for studying it in some detail. 'heoretically, there are a variety of reasons why farmers have adopted this practice. Insurance against the vagarPi.s of. weather. diseases, and pests is a major reason. By planting more than one crop in the samc field, the farmer is also maximizing moisture. maintaining soil fertility, and minimizing soil erosion, which are some of the serious drawbacks of monozultttral farming. Intercropping . . . offers unlimited opportunity to increase th." productivity of arable land, and research efforts should be mounted to tackle problems that limit the efficiency of the practice.

Even though multiol cropping systems have been considered important by farmers in many parts of the world for centuries, the interest of the research community has accelernted oniy in the past two decades. In the literature search cited in Table 1.1, tere were only 187 published articles up to 1960, but 359

351 352 MULTIPLE CROPPING SYSTEMS FUTURE PERSPECTIVES OF MULTIPLE CROPPING 353 papers were published from 1961 to 1970. In the decade of the 1970s there were and potential 1440 future cropping systems. Some methods for setting specific research published reports in the survey, and this trend continues. The majority of priorities are outlined in Chap. 13, but in the broader picture a look at the these research reports describe agronomic systems, interactions total among crop system is essential. The research emphasis species, crop interactions with the environment, placed on either intensive intercrop­ and the effects of cultural prac- ping or relay cropping. tices as well as that focused on intensive sequential systems, on multiple crop performance. It is this wealth of recent information and depends on learning (I) why farmers practice these systems today, (2) how its interpretation that causes many in the agricultural research likely and development is the practice or expanded use of these community to seriously examine systems in the future, (3) what constraints the future of mu!tiple cropping systems. are faced b, the farmer in improving food production and increasing profits in The future global importance of multiple cropping is difficult to predict. these systems. ,nd (4) how likely can research and development effors solve Current trends indicate an expansion in double cropping and other sequential these constraints (J. Sanders. Purdue University, systems in many areas, both in the developing world personal communication). There and in developed countries, isa need to examine these questions from the The points of view of several disciplines. potentials of short-cycle rice (Oryza sativa) and other cereal varieties have The future potential of multiple cropping to help made possible two or three crops per meet burgeoning worid year in areas with ample resources, such food demand needs as the intensive, high-input to be put into perspective by looking at the bioloeical po­ rice and catch crop patterns practiced in the Central tentials of these systems and the ecological and environmental consequences of Visayas of the Philippines. Yet the rapid expansion of mechaniza:ion and increase their use, as described in Chaps. 3, 4. and 5. Of in farm size has resulted in a reduction of intercropping equal importance are the or other intensive economic and social impacts of multiple multispecies practices in cropping systems, discussed in Chaps. the more climatically and edaphically favored parts of 1! and 12. Multiple cropping systems represent a response by farmers to pro­ developing countries. It is unlikely that intensive cereal/grain legume intercrops duction resource scarcity. as well as an attempt to maintain the lowest possible will expand in the near future except where there is a clear complementarity costs of production and most stable, least-risk between component species. strategies to produce food and income. To some degree, the expansion of multiple cropping systems There is ample evidence that some forms of intensive sequential or inten­ or relay' sification of their use will depend or, how research cropping systems will continue to expand: drives the technology or information base in this area aid ho\\ national political dec,:ioris encourage discourage the small-farni sect,r or Winter wheat (Triticwn sativun)/soybean (Glvcine ping in southeast United arl) double crop- The farther one projects into the States the future, the less confidence can be placed analysis. The previous chapters describe in detail the advantages of " Overseeding legume cover into growing maize (Z-1 nays), oybeans wheat. and imultiple cropping: more efficient and complete use of iesources " Strip cropping of maize.soybeans or sorghum (Sor,,ui such as solar beans energy. nutrients, and water; reduced risk with increased income sources: and greater biological diversity in crops and Double and triple cropping of high-value egetable crops stability ii, the cropping systems and the environment. Finite supplies oi- fossil fuels obligate us to carefully consider * Intensive use of relay and sequential systems in China and Southeast alternatives, and these Asia intensive systems appear to provide such biological ef­ ficiencies as reliance on nitrogen * Use of multistoried perennial and fixation, reduced pesticide use through eenetic perennial/annual crop mixtures in resistance and integrated Southeast Asia pest managcmen and potential biological production compensation by multiple * Alley cropping in West Africa and other species ir, a system. Thus. there are clear indications intensive terrace svst.ems. such that in some areas these intensive as those in Burundi svstems offer promise as innovative approaches to crop resource use that can be sustained and are appropriate for adequate long­ Thus. a number of intensive cropping systems are being practiced by both term food production. Multiple cropping systems provide a potential for the majority of farmers who operate in a low-resource situation. Research low-resource and high-technology farmers. both in the developed world in multiple and in cropping svsrtems anu the analysis of their applications developing countries. are both timely' and important in the overall strategy to meet world food needs. This importance warrants continued study of multiple cropping potentials. The evidence is that intensive cropping systems are not merely a vestige of the historical roots of crop culture, as eloquertly described by Plucknett and Smith in Chap. 2, but would appear to be increasing in importance in much of the BIOLOGICAL POTENTIALS OF MULTIPLE CROPPING world in specific situations where there is an economic. biological, environ- Research has shown that multiple mental, or social advantage cropping has several advantages over mono­ to this type of crop culture. culture under a range of circumstances. According to Swindale (19SI). inter­ In each of these production situations, it is important to examine current cropping 354 MULTIPLE CROPPING SYSTEMS FUTURE PERSPECTIVES OF MULTIPLE CROPPING 355 Appears to make better use of the natural resources of sunlight, land and water. It with increased resource use efficier..y, may have some beneficial effects agronomic sustainability, and thus greater on pest and disease problems.... and there is fm an advantage of mixing a legume with a nonlcgume to save on the use of nitrogenous food production security and its concomitant rewards (Greenland, fertilizers. 1975). Long­ term viability also depends on taking into account the environmental conse­ quences of the intensive resource use that comes from an Results from current research on crop rotations (Chap. 8). publications exploitation of these on biological potentials. What are some of these biological potentials? incidence (Chap. 9), and detailed physiology studies (Chap. 4) are beginning to The intensification of use of land and growth resources in the time dimension unravel some of the intricacies of these sytsems and explain how they function, is one obvious potential for multiple cropping. Although extended maturity of Yet many of the biological efficiencies of the systems have evolved over centuries individual crops can take advantage of certain entire temperature-favorable or as farmers, through a directed trial-and-error process, brought together new moisture-favorable growing seasons, especially in the temperate regions, there combinations of plant species and cultural practices to meet their needs (Fig. are many more options with shorter-cycle component 15.,). crops in multiple cropping systems. The soybean/winter wheat double cropping or relay cropping in the Plucknett and Smith (Chap. 2) have outlined some of the known and prob- able origins of multiple swinter temperate United States is a successful combination of a summer annual with a annual, which makes efficient use of both potential growing seasons ableoriinsof ultplcspecies systems. It is unlikelv that most farmers under- while stood why. in a biological sense, their systems produced more food at a lower maintaining vegetative cover on the land for mo.t of the year (angdaleL ea.,t~ risk. Yet they undoubtedly did ,inderstand the benefits of diversity and intensive 1984; Lewis and Phillips. 1976). Two- and culture of several crops three-crop rice patterns in the Phil­ together. This led to the development of a diversity of ippines and species combinations and practices for producing, them. By combinin,, and in- China. as well as rice/grain legume and rice!rice/grain legume sys­ tems are examples ot the same type of intensification in the tropics and subtropics tegrating the qualitative indigenous knowledge about cropping systems and the ,lvbre moisture rather than temperature may be most limiting (Gomez and Gomez. quantitative analytic techniques used in scientiric research, a clearer picture of 1983). A combination of summer grain crop (maize or soybean) with an over­ the biology of multiple cropping systems is possible. An understanding of the seeded relay' legume species which grows in fall and again in spring for nitrogen soil/plant/water environment, the potentials of newer crop genotypes, and im- production is another example of the concentrated use of time in agronoic proved management (Rao, Chap. 6) makes possible the development of systems systems (Hofstetter. 1984). Intensive cropping patterns use the growth resources and land area through the maximum possible period of the year. and thus result in as much dry matter and food as potentially can be produced by the tarmer -­_ Intercropping and relay cropping are examples of systems that make the most JI ".' efficient use of potential total grewing season. The intensification of land and resource , t !j1 use in the space dimension is another important aspect of multiple cropping, especially, with intercropping and relay -- sstems. Enhanced efficiency species that occupy the same landof incident light use is possible with two or more area during a significant part of the growing season and have a different pattern of foliage display (see references and dis­ cussion in Trenbath. Chap. 4). Different rooting patterns can explore a greater at ,.,total soil volume with roots of' different depths. These combinations of crops can result in tapping of deeper strata and bringing nutrients to the surface for succeeding crop cycles (larwood. 1984). When there are differences in the timing or intensity of uptake of critical growth elements (both nutrients and water) 7use from the soil, then some combination of species could make greater total of aVailable growth factors than would be possible irl with a single species in monoculture (Barker and Francis. Chap. 8). The several chapters on agronomic practices (Clhaps. 6 through S) give examples of these potentials in cereal grains. :. . legumes. and root crops. These biological potentials can be realized when in­ , terspecific competition Figure 15.1 Intercropped mixture of Xanthosoma sp., cassava (Manihot esculenta). pine- for grow th resources is less than intraspecific competition apple (Anana sp.), and Bixa orellana, in the same environment, and the result is greater resource use and overx ielding near Lazaro Cardenas. Teapa. Tabasco, Mexico. by thc multiple cropping system (Andrews. i972). (Photo by Dr. Stephen Gtiessman.) The intensification of resource use in both time and space is one of the 356 MULTIPLE CROPPING SYSTEMS FUTURE PERSPEuTIVES OF MULTIPLE CROPPING 357 ultimate biological potentials of multiple cropping s-stem. Different maturities provide a and rooting patterns biological control of damaging insect species. The diverse species of grossly differer .pecies provide an agronomic mix of present in a multiple-crop situation may promote and maintain plants which is far different from a monoculture in the same a wider range of place, and the these natural enemies due potential yields may be far greater. to the greater and more diverse habitats provided. A relay or intercropping system of maize There and sorghum may be less opportunity for an insect to land on a crop of choice, in Central America or of sorghum and pigeon pea (Cajanus cajan) when more than one crop is present in the field. "Visual in northern Nigeria illustrate the potentials of crops and chemical stimuli from and spatial which have different temporal both host and nonhost exploitation of growth factors (Rao, Chap. 6). These plants affect both the rate of colonization of herbivores systems can and their behavior" (Altieri and Liebman, Chap. 9). Again, these methods make use of an entire rainy season in a manner more efficient than of any known suppressing insect populations and mcnoculture. Their notentials could be compared reducing their damage can contribute to a to a double crop of one species nonchemical control or that makes use of the biological structuring of the system of two short-cycle species that could be grown in this type of rainfall to regime and internal resources on the farm. determine which alternative is most advantageous to the farmer. Combinations Diversity of crop species in an intercropping of annual and perennial species such as alley cropping maize, sorghum, or grain pattern gives a dispersion of potential host plants for pathogens that is similar to natural ecosystems. The legumes between strips of Leucaena or other woody legume illustrate both spatial differences and temporal complernentarity. in occurrence and damage from plant pathogens are not as striking nor as consistent as the differences Potentially important for the limited with insects (Altieri and Liebman, Chap. 9). resource farmer is the accumulative Yet there use of nutrients is evidence tht mixtures ofcrops buffer against losses to plant that are internally produced or available and that cvcle throu-h diseases; there may be reduced spore dissemination, delayed systems on the farm. Nitrogen fixed by a woody legume infection of plants. or mod­ species or by an annual ification of the microenvironment leguminous grain or green manure crop can provide in a way that reduces pathogen development a partial or complete alter- and economic loss. With a few diseases, this modification native to in microenvironment expensive and/or unavailable chemical fertilizer. Accumulated organic may promote greater pathogen spread and damage, but there are matter from intensive systems can provide additional nitrogen. fewer of these If carefully man- cases listed in the review aged. this can be a more sustainable (Chap. 9). A multiline variety of wheat or other cereal system, and one which might be called is 'regenerative" a parallel breeding solution to disease problems. and this is one approach in its improvement of the soil fertility resource for future cropping that could be used to diversifv a monoculture and seasons (Hanvood, 1983). promote this type of "'resistance" Another in the crop (Jensen. 1952). set of biological variables in multiple cropping involves the com- plexity of insect, Another biological reality is the complex set of physiological plant pathogen, and weed interactions discussed by Altieri and reactions of Liebman plants .khen grown in mixtures, as explored by Trenbath (Chap. 4) (Chap. 9). Potentials of multiple species systems, wheher intensified and reviewed in by Willev (1979a. 1979b). When greater total density is used time or space or both, appear to contribute to integrated pest management. in a mixture of Competition species. there is a greater total demand for resources, athough this with weeds from an increased density of crops or from a combination may be spread differently over time or space. This may result in stress of species occupying two or more niches in the cropping environment on one or more com­ can ef- ponents of the mixture or sequence: fectively reduce weed germination amd the stress may be different from that found growth, and thus increase crop produc- in monoculture. tivity without One example ;s the reduced light intensity on a lower expensie herbicide inputs. The potential of multispecies svstems, story as well crop, such as bean or soybean grovn under maize, while the as the upland/lowland rotations or wet season/dr-, season alternatine maize :uffers only from an increased competition for moisture culture in some parts of the tropics can contribute or nutrients. Careful examination of to .eed control , ith a cropping an intercrop pattern system and the ph\ sicai organization of the components could that is counter-cyclical to that of the weed species (Francis and Harwood. lead to ideas about how to bettcr arrange or sequence two or more 1985). The weeds that predciinte with one crop in the sequence crop species. More may be quite precise measurement of their different species from those in a succeeding yields, total dry matter production. and yield com­ crop, and thus their reproductive ponents could contirm these hypotheses and lead to design of more productive cycle may be broken. resulting in a cultural control of weeds, multiple cropping sN stems. Insect patterns may also differ in multiple species cropping s,stems corn- Breeding crop pared to -rionoculture. Although the same varieties or hybrids for complex systems presents some dif­ insects may be present. their distri- ferent challenges than breeding for monocuture bution (Francis. 19g5b: Smith and and reproduction appear to be altered by the mixture of species. This Francis. Chap. 10). There is a wide generally results in less damage to crops (Altieri and Liebman. Chap. range of traits that will be needed in new Q). There varieties for either system. These traits include general adaptation to temperature are a few cases reported where increased insect damae occurred in multiple and rainfall patterns in a region. cropping, but these repors are minimal. resistance to prevalent insect and disease prob­ A number of factors may explain why lems, insects and seed color and quality characteristics that are acceptable to the are inhibited by a multispecies system. There may be more natural producer ene- and the marketplace. Yet other traits mies-predators and parasites-in the association may be more important to success in an of crops, and these would intercrop: competitive ability, tolerance to stress under lower light levels or less 358 MULTIPLE CROPPING SYSTEMS FUTURE PERSPECTIVES OF MULTIPLE CROPPING 359 available moisture, ability to climb the maize in the case of indeterminate beans, with multiple cropping and efficient use of available nutrients, systems. since the limited-resource conditions of many farmers who practice multiple There also may be differences in the economic cropping systems may dictate a need for realistic and resource bases of the low-input farmers who predominate recommendations. This focus is quite different than the in the use o'these systems, and the crop quality factors emphasis at may be more important many experiment stations on high-input to the subsistence farmer. Productivity may be important. technology. but profitability These factors in the biological environment-crops, also must be considered by most farmers. Some production weeds, insects, and constraints which patogens--can be manipulated through agronomic have been identified cannot be solved easily through agronomic practices and genetic change. The several chapters that deal manipulation of the cropping system. When with agronomic and breeding approaches, plus plant breeding holds promise to those solve these constraints, on methodology for research, provide a survey of the an important focus must be on breeding objectives. and importance of the how these vary among biological potentials of multiple cropping systems systems. Although a number of the same traits may be and how to study them. To important for certain complicate the application of this information, the species in several systems, there will no doubt be economic and social factors a dif- involved in limited-resource agriculture, ference in the relative importance of these traits. often practiced by small farmers, must Since progress in a breeding be considered program is inversely proportional during the research and development process. to the number of traits for which selection is No biological po­ practiced, tential can be successfully exploited if the practices or varieties it is important to concentrate on those traits that are most are not accepted critical for by the farmer. These aspects success are explored in a later section. of the crop variety in the system of interest. The most evaluation in a breeding critical final program is testing new varieties in the system or systems of interest. These need to approximate as closely as possible the systems into ECOLOGICAL AND ENVIRONMENTAL ASPECTS which the varieties will be introduced. A logical OF ALTERNATIVE final step in the process is CROPPING SYSTEMS testing by farmers under their own farm conditions. The There are some obvious parallels between multiple species methodology for deciding on research priorities and for cropping systems and analvzing and Turay o ing palcommuni interpreting results has ties ofe ece (romris.st b)n been examined by Parkhurst and Francis (Chap. 13) and naturally occurring plant communities. These often include (from Francis, 1985b): by Nlead (Chap. 14). There are some unique differences and complexities in- I Genetic troduced into cropping systems by including more diversity in plant species than one species. The number 2 of potential Resulting diversity in the insect and pathogen populations interactions is increased vastly by increasing the number that are as­ in a system. and this of species sociated with ciops makes the choice of research problems even more critical 3 Na'r;ent cycles that are relatively than in monoculture research. There is some debate about closed. with much of the nutrient the optimum types or requirement combinations of of succeeding crops supplied by a previous crop experiments that should be utilized in the fie!d to efficiently or cover explore the questions crop residue (in low-input systems) of component technology in multiple cropping systems. 4 Veetative cover over the land through much At one end of the spectrum is the complex factorial of the year design with all factors 5 Hi,-h total use of aaiah"iul.t and water throu,zh the year because of included in at least two levels. This gives the maximum number of comparisons the presence and the most comprehensive evaluation of interactions of gro.ing crops in the svstems. At the 6 Low risk of complete h oof loss of crops in a given season or year because the different ecological other xtreme are simple experiments which niches they occupy and the different patterns study only of demand for growth factors Lime. with many of these experiments how carried out each season to get an idea of level to manipulate the many potential changes in a cropping system. This ives 7 High e nstionof productio t stabilityrc p (comparedt s to monoculture) as a result less information on interactions, although there is greater experimental control over each ponent fails trial and less potential loss if a few Careful reading of the two cited treatments are lost from trials. chapters will reveal advantages and disadvantages f;lc of "ach of these approaches, These characicristncs of multiple cropping systcms, and the best recommendation is probably to work especially those with with some reasonable two or more species together in the field at combination of factors in each trial, to explore the most the same time. make them desirable for the limited-resource farmer. The comparative important interactions, and then to move on to another series biological ad%antage of multiple of experiments in cropping systems tinder subsequent seasons. There a high-input situation is less dramatic. although the is a growing interest in designs and treatments that provide double cropping (winter wheat. soybean illustrated results as response surfaces rather tharn as or rice:rice), ratoon cropping [sugarcane comparison of (Saccharnm olf inmrun). discrete treatments (Barker e' al., 1985). It is sorghum, rice]. and relay cropping [maize/sesame critical to combine the research (Sesamunn on the experiment station indicum} or maize;soybean] of a number of commercial with testing under farm conditions to ensure that crops all information illustrate the benefits of these svstems and recommendations are relevant to the farmer. when resources are not limiting. This is important One of the widely debated theories in multiple cropping and ecology circles 360 MULTIPLE CROPPING SYSTEMS FUTURE PERSPECTIVES OF MULTIPLE CROPPING 361 is that greater genetic diversity leads to greater productivity. presents Hart (Chap. 3)-, evidence on both sides of the question, and gives examples of where this is not true. Systems with high , productivity, such as intensive rice or sugar cane production, are the result of high nutrient subsidy and low genetic diversity. Subsidizing a system with external resources-fertilizers, pesticides, irrigation water-can bring high levels of productivity through dominance of the production environment, but these systems are sustainable only at a high external cost. The diversity and cropping intensity of multiple cropping systems, especially intercrop an pattern such as maize/bean, can bring moderate to high levels of pro­ ductivity through manipulation and exploitation of the resources farm, and this can be sustained internal to *he at a lower cost (Francis and Harwood, 1985). In this way, the stability of production or sustainability over time in an intensive multiple species cropping system is similar to a natural ecosystem. The concept of energy and nutrient cycling is important in cropping systems that are designed for sustainability over a long period. In multiple cropping systems, and especially in low-input systems with reliance primarily on internal resource cycling, the increased production _..fcrop rsidues and their use by subsequent crops are important factors in promoting stability of production. Systems that are gaining in favor, such as minimum or conservation tillace ("ecofallow" production systems), conserve and rely on residues for reducin2 runoff losses of nutrients and moisture and for supplying organic matter and nutrients to crops in the next year. The cycling of carbon, nitrogen, phosphorus. potassium, and other elements in an agricultural system is promoted by those cropping patterns that include a range of species. especially w.,hen the crops are dissimilar in rooting patterns and growth cycle. The so-called "phosphorus pumping , activity sone can bring of deep-rooted species this critical nutrient up to the annual crop root zone and keep itcclin in the strata where needed. The preservation of a high proportion of nutrients in living and decaying organic matter also ensures that these nutrients will be available for subsequent crops rather than leaching down through the profile and being lost from the immediate crop environment (Fig. 15.2). This is low tropical rain forests and other natural ecosystems maintain fertility and plant gro%,th (N,­ and Greenland. 1960). Hart (Chap. 3), Harwood (1983). and Rodale (1983. 1985; further suggest that multiple cropping systems could apply what is known about natural eco­ systems, plant communities with their associated populations to design rmicraorganims. and plant useful alternative cropping '-stems that "ould meet the objectives of the farmer and be dependent r. understand how individual components on internal resources. It is critical to of technology that are proposed to im- prove a farmer's cropping system Figure 15.2 Multistored tree fit into the overall fa"rm crop agroecosysten with coffee, cacao, and Erythrina trees; note saphiny shade of the region. If this concept is taken of forest tree Cedrela mexicana in the right foreground, into accoun: in the cva!uation of new near C6rdenas, Tabasco, Mexico. (Photo technology. there is a greater by Dr. Stephen Gliessman.) chance th-it the eventual choice of new practices will be more ecologically sound and be more sustainable over time. Francis and Kauffman (1985) present a series of resource-efficient technologies that rely on internal resources and can apply both to large and to small farms. These include 362 MULTIPLE CROPPING SYSTEMS FUTURE PERSPECTIVES OF MULTIPLE CROPPING 363

fertility regeneration through multiple cropping and nutrient c)cling, pest pro- level specific. Multiple crop systems are not always more profitable. but they tection through species diversity in crops and genetic resistance, integrated pest do appear to be more stable over time and give a igo management, minimizing tillage and coexistence with a low level of weed pop- the farmer with a specified level of net incobabi onproviding ulation, mixed cropping of annuals and perennials, and integration of animals and Willey. 1980). Thus biological diversity appears to provide into the cropping/farming system. These factors all greater economic contribute to development stability. The economic diversification that results from multiple species plantings of systems that are more sustainable, in part through a mimic of natural eco- can also be achieved by planting a diverse series of crops in monoculture on the systems ineach area. same farm. These two strategies for providing greater stability need to be rec­ ognized and compared. ONOMIC AND SOCIAL IMPACT OF MULTIPLE CROPPING Structural changes inthe rural economy. such as prices of inputs, availability Discussion of economic and social factors must necessarily focus on two distinct of a market, and relative prices of commodities can influence the decisions of s Fietriys stic applicationsapic aions ofof theheconic concepts epts ofof multipleipl ce cropping.ro pping.t s nte the farm er on what crops to plant and in what proportions (Lynam et al.., Chap. First isthe intensive cash 11). Greater access to markets, wider availability of inputs such as fertilizers, grain double cropping or relay croppingof commercial crops inthe developed pesticides, and irrigation, plus credit or other government incentives to use these world or infavored areas of developing countries. Where these crops are grown inputs, can influence the farmer toward higher-technology approaches to food with high technology, adequate fertility and other inputs, and with mechanization production. This shift may result ina higher proportion of export crops and less Of planting, cultivation, and halvest, there islittle to distinuish the systems basic food production, a dependence on external resources that must be purchased from commercial monoculture, at least inthe economic and social sense. CreD- and transported ping decisions are made on costs of production and to the farm, a reliance on government participation and infra­ market factors, and the structure, and timely payment and favorable world market price for commodities commercial nature of these systems leads to decision ,naking that is similar in (Francis and Harwood. 1985). In spite of the apparent advantages of speciali­ most ways to decisions for monoculture systems, zation and the relative comparative advantage for producing one specific vell­ In the small-farm situations where most intercropping is practiced by farmers adapted crop. many farmers are currently short of food and income because they with limited resources, the economic and social situation is much different. The have deemphasized food and subsistence crops. complexity of these farming systems is due to the ;;any clirtological. bioiog- Also important are the sociocultural factors involved in the farmer's dcci­ ical, economic, and social factors that interact in the total small farm environment sions on type of cropping system to employ (Bradfield. Chap. 12). There are (Francis. 1985a). In addition to the complexity of these factors and their inter- strong psychological factors involved in the adoption of new technology. The actions, there is a wide range of objectives of the farm family, including pro- behavior of dutoof foodioand incomer minimonalg risk and Providion farmers is rational. but the extension aent and researcher must duction of food and income, minimizing risk and nroviding stabilitystablit peerhr is and s of produc- understand the total economic, cultural, and nutritional environment within which tin. and sustaining both foed and income through as much of the year as possible. decisions are made. This must all be accomplished with a minimal land resource and with limited There are institutional factors that influence decisions as well. High gov­ or no capital on many farms. Multiple cropping is one of the strategies that ernment prices, and thus incentives to produce cotton for export. may be viewed farmers use to meet these challenges, as a viable solution for income generation and purchase of food by small farmers. Lynam et al. (Chap. II) suggest that degree of market integration of the On the other hand, farmers may have had a previous experience ,%here markets farmer is important, and that there are few truly subsistence farms: most farmers have disappeared, or prices have gone down drastically, or government agencies in the developing world have some commercial and some subsistence objectives, have not delivered the needed inputs for production on a timely schedule. The and thus the consumption and production decisions are interrelated. They also faraer may be rational in rejecting the apparent short-term incentives to produce describe the uncertain nature of agriculture, and that with limited resources to this new export crop based on past experience that led to shortage of income invest in the production process and an uncontrolled environment, the farmer and food as a result of factors beyond the family's control. Many economists becomes more concerned with security and maintaining subsistence needs. In- expect that subsistence food production will become less important as agricultural tercropping is seen by the farmer as a strategy to achieve both biological and development moves ahead and markets become better developed and more stable. economic, as well as nutritional, diversity which has a better chance of sustaining Other factors in the governmental and political area may influence decisions the family through a wide range of variable and usually uncontrolled cropping to adopt or not to adopt a new technolo,,. Bradl seasons. teld (Chap. 12) presents the Profitability of the cropping example of a recommendation to introduce certain soil conservation, cropping h Potilityo croppong system depends on the biological success of pattern, or other technology' practices which would enhance the long-ternm fertility Crops complement each other over time. pr ofit hus i and npt-w status of the soil. Perhaps not known to the extensionist. the land ownership .t profit thus issite. time, and input- patterns, tenancy conditions, lack of credit to buy inputs, lack of assured markets 364 MULTIPLE CROPPING SYSTEMS FUTURE PERSPECTIVES OF MULTIPLE CROPPING 365 for the products, or lack of other infrastructure make the recommendation im- possible A growing body of information on agroforestry will become a useful or very difficult to adopt. This could easily cancel its obvious biological re­ source to the agronomist and research administrator interested in and physical environmental advantages in the region. Although many multiple crop­ new tech- ping systems. Thi': integration of the long-term nologies in developing countries were thought to be scale neutral in application, sustainability and contributions of forest species to food and income, and the close integration of annual crop they are still out of reach for the majority of farmers with limited resources, plants with The development perennials holds great promise for improvement of farmirg systems. of more productive intercropping techniques may in fact be In many areas where clear cutting of economic species has acurred, the scale-specific type of technology that will be well suited to the resource there is a base potential to regenerate a part of this forest resource and the muliple and complex needs of concurrently with develop­ the small farmer. ment of food crop growing potentials. There are hillside areas that are prone to FUTURE RESEARCH ;N MULTIPLE CROPPING erosion and nutrient and water loss where some combination of permanent or semipermanent trees with shorter-term economic crops would be highly desirable. Each of the preceding chapters has presented This field is receiving increasing interest and support in the research community, a section on future research in and the International Center for Research in Agroforestry' (ICRAF) in Kenya is multiple cropping from the perspective of an expert on that topic and discipline, leading efforts in this research. In this chapter an overview of research is presented from the perspective of total Agronomists and plant physiologists cropping and farming systems. The needs agree on the need for more research for research in broader aspects of on the components multiple of cropping systems and how the components interact in the cropping that transcend disciplines and require a team approach to use of growth resources. There may be additional data that can be research and extension would appear to be a valuable route to understanding collected from existing experiments that will make them complex systems, and to working with more useful in gaining an understanding farmers to improve them (Gilbert et al.. of how systems 1980). work. With yield trials of intercrops, the study of components of yield can often reveal some In the areas of ecology and environment, insieht on the timing of competition for growth there are a number of research resources et directions (Carter al., 1983). This can lead to new combinations or physical/ that could be pursued to develop more productive cropping systems in spatial organizations of crops that will reduce competition at a crucial the context of sustainability of food supply and regeneration of the production stage, or environment help the trop mixture compensate in some way for a reduction in one (Chap. 3 and 5). Continued study of natural ecosystems and component how crop. These studies of the detailed yield components plants interact in those systems can and biomass of an intercrop lead to basic information on crop competition, can complementation, also give the agronomist insight on system design and the breeder direction and interdependence. This information can be applied to crop- in setting priorities in a selection and testing program. and help ping systems in an attempt to make them more sustainable and more ecologicallv researchers focus on the most imporatt factors in the evaluation of new alternative systems sound than currently recommended and monoculture or available multiple species varieties. systems. The processes of soil fertility maintainance. nutrient cycling, and pest There is a serious need to investigate suppression are especially active svstems under conditions of low levels in natural ecosystems, and information from of this research production inputs and stress or the crops. Many of the most food-deficient could lead to useful clues about how to design cropping system areas of the world are in the arid and semiarid regions. and there has alternatives. The active and growing field of :.groccology is providing been less improved research carried out in these areas methodology for this research. than in more favorable zones. Efficient use Another of low level,, of resources may be more easily accomplished using fertile area for study is the identification and characterization of a mixture of species. and this could lead to new lower-risk strategies and cropping successful traditional and sustainable cropping systems systems sti!l used bv small farmers for the farner. (Gliessman et al., 1981: Chap. 5). This study could lead to an understandin, of Studies of weed interactions the vital elements of those systems that promote with crops are important to an understanding their productivity and success, of resource use and and provide competition for scarce moisture in multiple cropping systems. an information base to inform other farmers about successful and Research now in progress shows that low densities of weeds are proven practices. When useful practices and systems are characterized not necessarily and their harmful to yields, and may in fact contribute elements understood, this information can to organic matter and water and be combined with the practices that nutrient retention have come in the soil (Rodale Research Center. unpublished). This has from technical research into new or modified cropping practices that not been studied adequately in muitiple cropping systems. have a high probability of success. This combining of Root interactions also traditional knowled,ee are poorly understood in comparison with scientific approaches to gaining insight on to the wealth of information on competition their produciivit% and stability fr light. This is a promising and little-understood is area of competition, and an a new and premising avenue to pursue. Much of the current success of improved appreciation of rooting systems and uptake patterns monoculture technologies in the maize belt of the United would lead to States and otlier pro- design of genotypes and systems ductive that can take best advantage of scarce growth zones has come from the innovation of farmers combined with the potentials of modern technology. resources. Improvement of crop genotypes specifically for multiple cropping systems 366 MULTIPLE CROPPING SYSTEMS FUTURE PERSPECTIVES OF MULTIPLE CROPPING 367 sometimes will be necessary and sometimes not. There is no doubt that the University which will be current understanding another major contribution to this field (personal corn­ of intercropping potentials is constrained by the availability of lack of manication). varieties that have been developed for specific intercrop systems. The improved Finally. the use of simulation modeling has been genetic component has come directly from monczulture breeding sucested as a useful tool for multiple cropping research. When adequate programs, and thus there is no reason why it should be adapted data sets are available, or when to the different enough is known about types of interspecific competition that are crop species interactions and responses to major agro­ unique to intercropping. Although nomic some methodology practices to make informed assumptions vbout response has been proposed, there have been few programs imple- curves, then modeling becomes a potentially valuable menting these procedures in the field. The agronomist tool for the researcher. This does not will be saddled with this replace the field limitation for some time into the future. Current studies trial. Models can be used to simulate a wide ranee of new on genotype by cropping production alternatives, using different system combinations of inputs or techniques interaction do provide some insight on which species are more likely to which may better exploit resources demonstrate specific adaptation to multiple species cropping systems (Francis, internal to the farm. Given the complexity and number of factors in multiple cropping systems, simulation could 1985b). animportant nube here offcosi-utpecopn ytm.smlto ol beemr more than in monoculture research. The models can take A more generic question revolves around the applicability into account of other available long-term rainfall component technology from studies in monoculture and temperature data. and can project the relative success to the complexities of com- a of petition and resource near-infinite number of combinations of practices, genotypes, use in an intercrop. A systematic study is under way and combina­ (Francis, unpublished tions. From these, the most promising can be chosen for testing data) to statistically test a series of recommended tech.- in the field. As nologies the basic data set grows, so does the power and predictability and their interactions with cropping systems. This is analogous of the simulation to the exercise. This could be an efficient genotype by cropping system interaction evaluations. way to approach the complexity of site­ This study will lead to specific recommendations for small farmers v.ith different levels of limited some guidelines on which re­ systems, such types of results are :-!ost applicable to new cropping sources. as those with multiple species, and which technologics need to Successful application of multiple be developed and tested specifically for these cropping computer simulation models intensive systems, depends Several of on accurate selection of evaluation criteria. Much more the authors of these chapters cite the importance of on-farm needs to be research (OFR) done than to just measure or predict yield. biomass. and evaluation of new technologies by researchers working or net income. Food pro­ duction from the system, the distributioi together with farmers. The farming systems approach of food or income through the year. is mentioned frequently the labor as the methodology requirements for each alternative system, and the risk that which offers the most promise in this activity. There are would be many forms assumed, to name a few criteria, need to be included. of farming systems research (FSR). and almost as many These can be established interpre- through discussions with farmers tations as there are practitioners of the trade. Yet during the FSR approach. and can be modified a generalized ex erience is through subsequent runs with the computer. emerging from The farmer can he given a list of this activity, and it is one that will be useful for multiple cropping potential consequences of a given set of practices. research.When the search for successful traditional For example. if this new technology is combined with variety evaluation of is planted on this date with these other two species. the effect current constraints to production, and when the farmer is directly on yield. involved with the income, food supply. risk of no food, and lone-term- fertility implications could choice of alternatives and the field testing. there is a high probability be detailed, for this and alternative practices as compared that the right questions will be answered and the technologies x."]ll withos uldellthe be current variety and practices. The modeling approach appropriate and adopted. The feedback activities that are emphasized notc,pelltested. but is in this just in the conceptual stage process are also critical to its long-term success. A functional for multiple cropping. Given the power of the and rewarding microcomputer. there association is thus created between is no reason why this type of analysis could not be run. a rnd on-fa the people involved in research, extension. rm a pp lic ation of results. iven proper softare and instructions on how to modifv it. people f w r n n t u t o s o o by workin, at any experiment station oi . "is- p o l o k n There is a continuing or regional extension office. This is one need to develop more efticient evaluation tools for tool that mav soon be available to the researcher. extensionist. and farmer. on-farm research and testing, and the elaboration of minimum give the relevant data sets that will information without unnecessary. though interestin,. details FUTURE PROJECTIONS FOR MULTIPLE on systems and f .aes CROPPING who are participants. The emerging methods for as­ sessing research priorities will be useful for multiple cropping systems, as well In projecting the as for other research areas. The development future importance of multipie cropping systems in different and articulation of new or revised regions statistical techniques of the world, it is necessary to !ook at past trends and are powerful contributions to the researcher's set try to anticipate of tools any modifications to those trends to effectively evaluate multiple cropping systems. in the future. There is no question about the In addition to the review by influence Mead of mechanization on rural population and labor required (Chap. 14), ticre is a book in preparation by Dr. W. Federer at Comell in agriculture. This has promoted greater labor use efficiency and expansicn of monoculture. 368 MULTIPLE CROPPING SYSTEMS FUTURE PERSPECTIVES OF MULTIPLE CROPPING 369

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