Rural Homegardens in Central Sulawesi, Indonesia: An Example for a Sustainable Agro-Ecosystem?

Abstract

Homegardens are regarded as a species-rich agro-ecosystem located around a homestead for subsistence production and income generation. Often continuously cultivated over many decades, they could be considered as a model for sustainable agricultural production systems. As sustainability can not be assessed per se, certain indicators have been used instead, e.g. soil quality parameters or biodiversity. Plant diversity is considered as a basis for homegarden productivity and sustainability, however, it is not static over time. Agro-ecological and socio-economic factors that influence plant diversity are not yet fully investigated. The sustainability of homegardens has rarely been examined quantitatively or in a time series.The main objective of this study was to assess the sustainability of selected rural homegardens in Central Sulawesi, Indonesia. Certain sustainability indicators were used, emphasising plant species diversity, soil quality, and garden management. Factors influencing plant diversity were determined. Potentials to improve homegarden productivity and their suitability for in situ conservation of plant genetic resources were also assessed.The research was carried out in five villages of the Napu valley, Central Sulawesi, from each of which ten households were randomly selected. Three villages were mainly inhabited by locals, two by migrants. In all homegardens, the number and abundance of crop species (i.e. all useful plant species) were quantified for calculation of several diversity and similarity indices. For assessing temporal dynamics of crop diversity, 30 homegardens in three of the villages, which had previously been investigated in 2001, were re-inventoried in 2003 and 2004. Soil samples were taken in all homegardens to analyse physical and chemical quality parameters. Some of these soil analyses were also performed in the 2001-study. Gardeners were especially interviewed about homegarden management and plant utilisation. Cluster, multiple linear regression, and principal component (PCA) analyses were applied.The homegardens studied were cultivated for periods between 2 and 40 years, their cropped areas varied from 300 to 2,400 m2. The primary function was subsistence-oriented production of non-staple food, but some gardens were largely used for income generation. In both subsistence and market-oriented homegardens, the production potential was not fully exploited. Homegardens were mainly worked by women, but men were mostly responsible for fruit trees and cash crops. The used planting materials were largely of endogenous origin. Industrial fertiliser was more frequently used by migrant than by local gardeners. Insecticides were mainly applied in market-oriented gardens, herbicides also in subsistence gardens.In 2004, a combined total of 206 crop species were cultivated in the 50 homegardens studied, including many wild and under-utilised species. Besides, 162 ornamental and 58 weedy species were found. On average, 33 49 crop species were cultivated per garden. Composition as well as richness and diversity of crops differed markedly among the five villages. In the three local villages, species richness and diversity were rather high and vegetation structure more complex as compared to the two migrant villages. Cluster analysis based on species abundances partly reflected these differences. Multiple regression analysis revealed the most important factors that influenced crop species richness and diversity (positively, garden size ; negatively, cash-oriented production , migrant gardener ). PCA applied to the 30 re-inventoried gardens showed that crop species composition shifted towards more cash crops in villages with a relatively good market access. In these three villages, overall crop species richness and diversity increased slightly from 2001 to 2004, which partly may have been caused by activities of development projects in the area.Soil quality parameters were highly variable within and among the homegardens surveyed. Soil erosion was considered as problematic in some of them. Over time, soil pH values as well as C and N contents decreased significantly; available P content showed a similar trend. This was, most likely, due to insufficient soil quality management.In conclusion, the homegardens surveyed were considered to be sustainable in socio-economic and crop diversity dimensions, but not concerning soil quality maintenance. In the future, sustainability of these gardens may additionally be threatened by different aspects of modernisation , such as an increased use of exogenous inputs and a shift towards cash-oriented production. To maintain the sustainability of these homegardens and their suitability for in situ conservation of plant genetic resources, any promotion to intensify production should consider to keep the structure and functioning of this agro-ecosystem.