OR IS IT THE OTHER WAY ROUND?
P. K. R. Nair
School of Forest Resources and Conservation
University of Florida, Gainesville, Florida 32611, USA
| ABSTRACT
The terms multistrata systems and homegardens that are used synonymously for the purpose of discussion in this paper represent a group of seemingly sustainable and profitable agroforestry systems in the tropics. Although practiced for a long time, the systems have been little studied, most reported studies being descriptive limited to identification of plant species involved and other location-specific information on their yield and management. Conventional mass-balance approach to estimating the extent of nutrient cycling in some of these systems have raised alarms about potential danger of excessive rates of soil-nutrient depletion from the systems and their consequent unsustainability. Yet, in the field, the systems seem to defy such predictions. Furthermore, these systems that provide sustenance to millions of farm families defy the market-superiority paradigm of neoclassical economics. These contradictions arise, perhaps, from our failure to understand the systems in their right perspectives. The methods and criteria that are used for assessing the productivity and profitability of market-oriented, single-species, agricultural and forestry enterprises may not be appropriate for understanding the ecological and economic "mysteries" of the time-tested multispecies systems. These systems can offer much to our efforts in developing sustainable agroforestry systems; but new initiatives are needed for accomplishing that. The efforts should start with a base-line assessment and collection of basic statistics on the area and number of people involved, and proceed with development of appropriate methodologies, much the same way as agroforestry research was initiated more than two decades ago.
|
In this presentation, I wish to stay away from the definition quagmire for two reasons. First, it is my conviction that it is impossible to define the entities that we try to define. For example, I have not seen a flawless definition of agriculture or forestry, let alone agroforestry. Secondly, and perhaps more importantly, I believe that a flawless definition of the entities we are working with is not necessary to make progress. The lack of a definition of a flawless definition of agriculture or forestry, or even agroforestry, has not hampered its development. However, we need to be clear about what we are discussing. The concepts should be clear. The characteristics of the systems or the entities that we are working on should be described. From that perspective, I believe that a clear-cut distinction does not exist between multistrata systems and home gardens. We cannot clearly establish the boundaries between the two establishing firmly where homegardens end and multistrata systems begin or vice versa. The farmers may not be keen about such academic issues and the researchers do not universally recognize or follow a clear-cut demarcation between the two systems. What is referred to as homegardens in some situations may be referred to as multistrata systems in another, and vice versa. So, a clear-cut distinction between the two types of systems is not feasible or realistic, not even necessary. Therefore, in this presentation, the word homegarden is used in a generic sense to include homegardens and similar other multistrata agroforestry systems, where there are multiple species and naturally multiple layers of aboveground and belowground plant parts, and consequently interactions between and among them in sharing of growth resources. And, all the other nice and not-so-nice attributes of agroforestry systems that we all talk about. What I would like to do in this presentation, though, is to think aloud if or to what extent we have been able to understand scientifically the functioning of these fascinating systems, and what direction we should be taking in focusing our future research attention in this area. Tropical Homegardens: A Scientific Mystery? Tropical homegardens have provided sustenance to millions of farmers, and prosperity to some, around the world, for centuries. They have fascinated the scientists too for quite some time. However, the extent of scientific studies on these systems has been disproportionately lower than what their economic value, ecological benefits, or sociocultural importance would warrant. And, the few studies that have been made have produced more questions than answers to the "mysteries" of these systems. Yet, homegardens flourish today almost unchanged from the pre-scientific-agricultural days, and may continue to do so for a long time perhaps without the incursion of science. It is hard to believe that homegardens defy science. So, is it that science eludes homegardens, or, perhaps, truer still, the methods that we employ for the study of homegardens are inappropriate? Ecological Mystery Based on our understanding of the ecology of mixed tropical plant communities, we believe that the tropical homegardens and multistrata systems are ecologically sustainable. The trade off between high species-diversity and low "export" of harvested products out of theses species is the main rationale for this belief. Based on this conviction, it is argued that structurally and functionally these multistrata systems are the closest mimics of natural forests yet attained (Lefroy et al., 1999). And, natural forests and other naturally occurring ecosystems are considered to be long-term products of evolution and the accommodation of organisms to environment, for they change with time as both environment and biota change and they run on solar power thus making them self-sustaining (Ewel, 1999). However, little is known about the ecological functioning of these multistrata systems. Most reported ecological studies on these systems are descriptive, often containing long lists of plant names in various languages and descriptions of their characters and uses, and sometimes accompanied by schematic diagrams of system structure and configuration. For example, the excellent, annotated bibliography and evaluation of homegarden literature until 1984 by Brownrigg (1985) lists several hundred references. Practically all of them are descriptive reports of the type, nature, and benefits of homegardens in different parts of the world. It is indeed a very valuable compendium that illustrates the diversity, complexity, and value of homegardens; but it concludes with a call for research on removing the ambiguity surrounding the homegardens as a development tool. The proceedings of the 1985 international conference on homegardens in Bandung, Indonesia (Landauer and Brazil, 1990), also gives predominantly descriptive accounts of homegardens, but include a few papers that are more analytical in nature. A literature search of publications on homegardens since 1990 yielded 30 citations, all of which are descriptions of existing systems in different places. Nair’s (1989) synthesis of tropical agroforestry systems resulting from ICRAF’s global inventory of agroforestry systems contains a few homegarden descriptions; although they present the structure and economic value of those systems in some detail, they too are inadequate to understand the "mysteries" of the systems. Lok (1998) presented an excellent compendium of multidisciplinary analysis and characterization of the homegardens of Central America. Some other researchers who have been active in the subject such as O. Somarwoto (e.g., Somarwoto, 1987) and G. Michon and colleagues (e.g., Michon and deForesta, 1999) deal mostly with an"architectural analysis" of homegardens replete with various types of schematic diagrams. Thus, we have a fairly good understanding of the essential characteristics of the major types of tropical homegardens. It may not be too far from reality to state that all tropical homegardens are similar in their structure and function. All of them involve an intimate association of different plant taxa forming a multistoried configuration of canopies, and together they provide an enormous array of useful products mostly for home consumption. The root systems of the different components of the system are presumed to be overlapping such that the system provides a much higher root-length density (cm roots per cm3 of soil) than in any monocultural system, although quantitative data on this point are scarce. Even the more quantitative studies dealing with soil fertility and plant nutrition have not contributed substantially to our understanding of the intricacies of these systems. These studies mostly follow a general pattern: they start with the assumption that homegardens are ecologically stable and sustainable systems characterized by highly efficient nutrient cycling, and then create nutrient budgets according to "conventional" mass balance approach with estimates of inputs and outputs. Invariably all such estimates have led to high rates of nutrient outputs from the system implying that the systems in the long run will deplete the soil of its nutrient store and make the systems ecologically unsustainable. For example, Table 1 summarized from Beer et al.’s (1998) comprehensive review of shaded perennial systems gives the reported (high) quantities of nutrients involved in various phases of nutrient cycling in such systems. Fassbender (1993) and Nair et al. (1999) presented nutrient budgets of the shaded perennial systems that indicate substantially high amounts of nutrients being "lost" or "unaccounted for" from the systems (see, for example, Table 2). A recent study (McGrath, 1998) of an eight-year-old multistory agroforestry system in Acre, Brazil, reported, for example, that P removal from harvest of agroforest products was half that expected for pasture and shifting cultivation, and cautioned that N removal rates (in harvested products) were so high that N deficiency would eventually limit system’s productivity (Table 3). Yet, homegardens have flourished for a long time even near that study site without any apparent symptoms of soil-nutrient-depletion. Indeed, homegardens and other multistrats systems present an ecological "mystery." Economic Mystery Homegardens are a puzzle to the economist too. Early workers in agroforestry economics argued (e.g., Raintree, 1987; Hoekstra, 1990) that most traditional agroforestry systems followed the classical political economic theory of "basic-needs" approach, which states that goods have value because people find them useful in satisfying needs for food, shelter, or clothing. However, the "market superiority" premise of the neoclassical economics has replaced this theory in most enterprises. It states "it is only for the sake of profit that any man employs his capital in the support of an enterprise, and he will therefore endeavor to employ it in the support of value or to exchange for the greatest quantity of goods or money." Today, the economic efficiencies of farm enterprises are calculated based on their profit generation. Home gardens and other multistrata systems that are primarily subsistence systems, which fulfill the basic needs of farm families (mostly food), rank very low in the value premises and theoretical assumptions that underline the neoclassical analysis (Current et al., 1995). Thus, the homegardens are a mystery to the economists too in that these systems that have flourished for a long time defy the economic standards and criteria that are widely used for measuring the efficiency of land-use systems and other production enterprises. Some of the socioeconomic "stigmas" attached to homegardens are now being corrected. For example, the notion that homegardens are practiced only in areas of acute land shortage has been debunked. In a comprehensive investigation on the development of intensive multistrata agroforestry system in Tomé Açu, in the eastern Amazon region of Brazil, Yamada (1999) chronicled how motivated Japanese settlers developed economically and ecologically successful multistrata systems in a region of no land scarcity. Yamada’s investigation also reported extremely higher economic advantages of multistrata agroforestry systems in comparison to cattle ranching and other "well established" land-use systems of the region. For example, a 10 to 20 ha agroforestry farm agroforestry farms generated net income comparable to that of a 1,000-ha pasture/cattle ranch. Furthermore, the agroforestry farms provided more rural employment per area especially for women, and posed no threat of deforestation, an essential condition for pasture establishment. The Reality The reality could be that earnest efforts have not been made to unravel the "mystery" of homegardens. First of all, multispecies systems have been ignored by the conventional wisdom of compartmentalized approaches to agricultural (and other land-use-system-) studies and development that have primarily been fossil-fuel-based. Even when multispecies and integrated systems (example: agroforestry) came to be recognized as useful development pathways, development vehicles were fueled by concerns about "burning" issues such as shortages of food and other basic needs and environmental problems (deforestation, soil erosion, and so on). The shining, time-tested examples of systems such as homegardens that provide sustained production of basic needs and environmental protection (Nair and Sreedharan, 1986; Bangaldesh systems reported in a series of articles in Agroforestry Systems: e.g., Hocking et al., 1997) were largely ignored or belittled. Their labor-intensive nature and occurrence in small parcels of land mostly in regions with relatively good rainfall or water availability posed problems to development experts who always look for technologies that are "new" and can be extrapolated to larger scales of land areas and inhabitants. The relative "prosperity" of the regions where homegardens are abundant such as Java in Indonesia and Kerala in India (compared to the rest of the regions of the countries concerned), and perhaps the lack of social and political might of homegardeners, may have contributed to this neglect. Furthermore, homegardens did not get cited in development chronicles because they represented traditional ways and indigenous species that did not receive development support or the attention of other "modern" approaches, and therefore were not considered as success stories. The good thing, though, is that in spite of the neglect by development specialists, these systems are under no apparent production- or environmental threats. The real losers are not the homegardens or homegardeners; it is the scientific and development community that has missed the boat: by learning about and unravelling the "mysteries" of homegardens, several valuable lessons could have been learned and even mistakes avoided. Hopefully, it is never too late to learn from new experiences and correct the past mistakes! The Way Ahead in Homegarden Research Any concerted international effort on homegarden development should start with learning about the intricacies of these time-tested systems. This will involve research for improving homegardens as well as applying the lessons learned from homegardens to the improvement of other such productive and sustainable systems. To start with, we should put a moratorium on producing qualitative reports that simply eulogize the virtues of homegardens. We should focus on compiling the "vital statistics" of the systems at local, regional, national, and global levels: area, production, income generation, employment generation, and such primary information. This will start with developing methods that are applicable in a wide spectrum of situations for collecting such information. Without these statistics, we cannot make any headway in impressing highest-level policy makers and thus attracting much-needed research funds. Research should then move on from the "beaten track" of species listing, profile descriptions, and spasmodic nutrient cycling estimates, to rigorous efforts in understanding the ecological and social basis -- the how and why -- of the functioning of homegardens. Conventional nutrient cycling studies and economic analyses that have proven to be inappropriate for homegardens should give way to innovative and appropriate methods that have the scientific rigor as well as the required depth and breadth to truly handle the "real" situation. The important role of the relatively high quantities of standing biomass in homegarden and other multistrata systems in carbon sequestration in soils (Schlesinger, 1999) is, for example, an area that has not even been considered in research. It could well be that one reason why the nutrient cycling estimates in multistrata systems do not reflect the reality is that the role of carbon sequestered as soil organic matter and its influence on the rate and extent of availability of plant nutrients are not factored into such estimates. Evidently, a new look at methods of data collection and interpretation related to multistrata systems is necessary. And, if the past decade’s experience with alleycropping research is any indication, we should try to understand why and how farmers do adopt their practices, rather than why they do not, and build that component into the technology generation. In a way, the strategy for future research in homegardens ought not to be different from what was followed for agroforestry research in the past two decades. Under the aegis of an international initiative, we need to collect "base-line" information on the extent, role, complexity, and importance of existing homegarden systems, identify research topics and procedures, establish interdisciplinary research protocols, promote rigorous research for solving the identified problems and making improvements in existing systems and/or designing new ones, and disseminate the research results to relevant clientele. Is the international donor and research community ready for that? Will this conference set the stage for that? REFERENCES Beer, J., Muschler, R., Kass, D., and Somarriba, E. 1998. Shade management in coffee and cacao plantations. Agrofor. Syst. 38: 139-164. Brownrigg, L. 1985. Home Gardening in International Development: What the Literature Shows. League for International Food Education, Washington, DC. Current, D., Lutz, E., and Scherr, S. (ed) 1995. Costs, Benefits, and Farmer Adoption of Agroforestry: Project Experience in Central America and the Caribbean. The World Bank, Washington, DC. Ewel, J. J. (1999) Natural systems as models for the design of suitable systems of land use. Agroforestry Systems (in press). Fassbender, H. 1993. Modelos Edafológicos de Sistemas Agroforestales, 2nd Ed., CATIE, Turrialba, Costa Rica. Hocking, D., Sarwar, G., and Yousuf, S. A. 1997. Trees on farms in Bangladesh. 4. Crop yields underneath traditionally managed mature trees. Agrofor. Syst. 35: 1-13. [Also see Agrofor. Syst. 25: 193-216 (1994) and 33: 231-147 (1996) for related papers by the same group of authors.] Hoekstra, D. A. 1990. Economics of agroforestry. In: MacDicken, K. G. and Vergara, N. T. (ed), Agroforestry: Classification and Management, pp. 310-331. John Wiley, New York. Landauer, K. And Brazil, M. (ed) 1990. Tropical Home Gardens. United Nations University, Tokyo. Lefroy, E. C., Hobbs, R. J., O’Connor, M. H., and Pate, J. S. (ed) 1999. Agriculture as a Mimic of Natural ecosystems. Special Issue of Agroforestry Systems (in press). McGrath, D. A. 1998. Ecological Sustainability in Amazon Agroforests: An On-Farm Study of Phosphorus and Nitrogen Dynamics Following Native Forest Conversion. Ph D Dissertation, University of Florida, Gainesville, FL, USA. Michon, G. And deForesta, H. (1999). Agro-Forests: Incorporating a forest vision in agroforestry. In: Buck, L. E., Lassoie, J. P., and Fernandes, E. C. M. (ed), Agroforestry in Sustainable Agricultural Systems, pp. 381-406. CRC Press, Boca Raton, FL. Nair, M. A. And Sreedharan, C. 1986. Agroforestry farming systems the homesteads of Kerala, southern India. Agrofor. Syst. 4: 339-363. Nair, P. K. R. (ed.) 1989. Agroforestry Systems in the Tropcs. Kluwer, Dordrecht, The Netherlands. Nair, P. K. R., Buresh, R. J., Mugendi, D. N., and Latt, C. R. 1999. Nutrient cycling in tropical agroforesty systems: Myths and science. In: Buck, L. E., Lassoie, J. P., and Fernandes, E. C. M. (ed), Agroforestry in Sustainable Agricultural Systems, pp. 1-31. CRC Press, Boca Raton, FL. Raintree, J. B. (ed) 1987. D & D User’s Manual: An Introduction to Agroforestry Diagnosis and Design. ICRAF, Nairobi, Kenya. Schlesinger, W. H. Carbon sequestration in soils. Science 284: 2095. Soemarwoto, O. 1987. Homegardens: A traditional agroforestry system with a promising future. In: Steppler, H. A. and Nair, P. K. R. (ed), Agroforestry: A Decade of Development, pp. 157-170. ICRAF, Nairobi, Kenya. Yamada, M. 1999. Japanese Immigrant Agroforestry in the Brazilian Amazon: A Case Study of Sustainable Rural Development in the Tropics. Ph. D. Dissertation, University of Florida, Gainesville, FL., USA.
Introduction
Table 1. N-dynamics data from some shaded perennial systems in Central America.
| Process / System | Quantity (kg ha-1yr-1) | Reference | |
| N2 fixation: | by shade trees in coffee/cacao plantation | 35 to 60 | Escalent et al. (1984) |
| by E. poeppigiana | 60 | Fassbender (1987) | |
| N2 release: | from coffee/cacao plantation w/ 120 to560 leguminous shade trees | 60 to 340 | Beer (1988) |
| through nodule senescence and decomposition of unpruned E. poeppigiana | 57 to 66 | Escalent et al. (1984) | |
| N mineralization: | in Costa Rican coffee plantation shaded by E. poeppigiana | 148 | Baddar and Zak (1994, 1995) |
| in Costa Rican coffee plantation unshaded | 111 | Baddar and Zak (1994, 1995) | |
| N leaching: | from shaded coffee plantation | 5 to 9 | Imbach et al. (1989a) |
| from unshaded coffee plantation | 24 | Baddar and Zak (1995) | |
| in typical tropical agroecosystem | 50 to 100 | Imbach et al. (1989b) | |
| N turnover: | though E. poeppigiana nodule senescence and decomposition | 9.6 to 50 | Nygren and Ramirez (1995) |
Table 2. Biomass production, turnover and recycling index for four shaded perennial-crop systems in Costa Rica.
| Component |
|
|||
|
Erythrina
+ coffee |
Cordia
+ coffee |
Erythrina
+ cacao |
Cordia
+ cacao |
|
| Fine root biomass, Mg ha-1 |
2.6
|
4.5
|
3.8
|
7.0
|
| Standing biomass, Mg ha-1 |
35.4
|
37.1
|
44.5
|
63.7
|
| Turnover, Mg ha-1 |
20.0
|
5.7
|
22.9
|
11.4
|
| Recycling, % |
56.4
|
15.3
|
51.4
|
17.9
|
| N in standing biomass, kg ha-1 |
522.0
|
286.0
|
357.0
|
400.0
|
| N turnover, kg ha-1 |
461.0
|
114.0
|
447.0
|
169.0
|
| N recycling, % |
88.3
|
40.0
|
125.0
|
42.3
|
| P in standing biomass, kg ha-1 |
46.0
|
34.0
|
38.0
|
50.0
|
| P turnover, kg ha-1 |
35.0
|
7.0
|
40.0
|
24.0
|
| P recycling, % |
76.1
|
21.5
|
105.0
|
48.0
|
| K in standing biomass, kg ha-1 |
338.0
|
229.0
|
428.0
|
346.0
|
| K turnover, kg ha-1 |
260.0
|
54.0
|
177.0
|
73.0
|
| K recycling, % |
77.0
|
23.5
|
41.3
|
21.1
|
Calculated from Fassbender (1993). Source: Nair et al. (1999).
Table 3. Biomass, stores, and cycling of C, N, and P in an Amazonian agroforestry system+ in Acre, Brazil during the eighth year after establishment.
|
|
|
|
|
|
| Agroforest Stores (g m-2) | ||||
| Soil (0-20 cm) |
204,000
|
4,906
|
418.2
|
102.00
|
| Total live above-ground |
3,415
|
1,640
|
25.0
|
2.15
|
| Total below-ground (roots, 0-40 cm depth) |
711
|
242
|
6.9
|
0.35
|
| Total above- and below-ground |
4,126
|
1,882
|
31.9
|
2.50
|
| Agroforest floor surface litter |
775
|
319
|
8.9
|
0.41
|
| Below-ground litter (0-15 cm) |
407
|
126
|
3.6
|
0.21
|
| Annual flux (g m-2 yr-1) | ||||
| Total NPP and N & P requirement |
3,042
|
1,368
|
29.3
|
2.20
|
| Reabsorption before abscission |
-
|
-
|
6.3
|
0.37
|
| Total return to soil |
1,256
|
507
|
17.5
|
1.24
|
| Uptake (requirement-reabsorption) |
23.0
|
1.83
|
||
| Outputs: removal from harvest |
466
|
223
|
4.4
|
0.40
|
| Inputs: rainfall/deposition |
-
|
-
|
0.6
|
0.01
|
+ System consisting of peach palm (Bactris gasipaes), Cupuaçu (Theobroma grandiflorum) and Brazil nut (Bertholletia excelsa)
Source: McGrath (1998).