CHAPTER ONE
1.0 INTRODUCTION
Self-sustaining, low-input, and energy-efficient agricultural systems in the context of sustainable agriculture have always been in the centre of attention of many farmers, researchers, and policy makers worldwide (Altieri et al., 1983; Altieri, 1999). However, most practices of modern agriculture, e.g. mechanization, monocultures, improved crop varieties, and heavy use of agrochemicals for fertilization and pest management, led to a simplification of the components of agricultural systems and to a loss of biodiversity. Restoring on-farm biodiversity through diversified farming systems that mimic nature is considered to be a key strategy for sustainable agriculture (Jackson et al., 2007; Scherr and McNeely, 2008). On-farm biodiversity, if correctly assembled in time and space, can lead to agroecosystems capable of maintaining their own soil fertility, regulating natural protection against pests, and sustaining productivity (Thrupp, 2002; Scherr and McNeely, 2008). Biodiversity in agroecosystems can be enhanced in time through crop rotations and sequences in space through cover crops, intercropping, and agroforestry (Altieri, 1999; Malézieux et al., 2009). While modern agriculture has brought vast increases in productivity to the world’s farming systems, it is widely recognized that much of this may have come at the price of sustainability (Tilman et al., 2002; Lichtfouse et al., 2009). This is because modern farming systems imply the simplification of the structure of the environment over vast areas, replacing natural plant diversity with only a limited number of cultivated plants in extensive areas of arable monocultures (Vandermeer et al., 1998). By contrast, on farm biodiversity is familiar to traditional farmers mainly in developing countries, where traditional farming systems are characterized by their great degree of genetic diversity in the form of mixed cropping and agroforestry patterns, based on numerous varieties of domesticated crop species as well as their wild relatives (Altieri, 1999). These farming systems offer a means of promoting diversity of diet and income, stability of production, reduced insect and disease incidence, efficient use of labor, intensification of production with limited resources, and also maximization of returns under low levels of technology (Anil et al., 1998; Malézieux et al., 2009). Intercropping, also referred to as mixed cropping or polyculture, is the agricultural practice of cultivating two or more crops in the same space at the same time (Andrews and Kassam, 1976; Ofori and Stern, 1987; Anil et al., 1998). The component crops of an intercropping system do not necessarily have to be sown at the same time nor they have to be harvested at the same time, but they should be grown simultaneously for a great part of their growth periods. In intercropping, there is normally one main crop and one or more added crop(s), with the main crop being of primary importance for economic or food production reasons. The two or more crops in an intercrop normally are from different species and different plant families, or less commonly they may be simply different varieties or cultivars of the same crop, such as mixing two or more kinds of wheat seed in the same field. The most common advantage of intercropping is to produce a greater yield on a given piece of land by achieving more efficient use of the available growth resources that would otherwise not be utilized by each single crop grown alone. There are many different kinds of species that can be used for intercropping such as annuals, e.g. cereals and legumes, perennials, including shrubs and trees, or a mixture of the two (annuals and perennials). In the case of shrubs and trees the term mostly used is agroforestry. The objective of this paper is to provide an overall view and evaluation of annual intercropping, summarizing its main advantages supported by a number of key examples from the published literature which point out its great value in the context of sustainable agriculture. This paper focuses on relay intercropping and not on agroforestry using garden egg and fluted pumpkin intercrop as case study.
The objective of this study is to evaluate the influence of intercropped telfairia and its time of intercropping on the growth yield of garden egg.
Meaning of Intercropping
Intercropping is the practice of growing two or more crops in close proximity and it is practiced by majority of farmers in the tropical and subtropical regions of the world. The system is widely practiced because it suppresses weeds and reduces pest disease infestation. (Ibeawuchi, 2007).
The degree of spatial and temporal overlap in the crop or more crops can be varied. As a result, numerous types of intercropping in which the temporal and spatial mixture have been varied to some degree have been identified (Andrews and Kassam, 1975).