The choice of crop species, varieties and their likely performance
For both genders, the growth of vegetables on allotments is controlled by the desire to grow potatoes. There is a key requirement to avoid repeated growth of potatoes on the same ground each year, to avoid the build up of two major pest species of potato cyst nematode (Globodera rostochiensis and G. pallida) (Winfield, 1990). This necessitates the development of a crop rotation on most allotments (Perez-Vazquez and Anderson, 2000), such as the example in Figure 20.4.
There is generally an increasing diversity of crop species and varieties within species seen on allotments in Britain, reflecting not only gender differences but also an increase in the ethnodiversity of participants (Garnett, 1996a; Perez-Vazquez and Anderson, 2000). The use of greenhouses or simple cloches means that people can grow food in allotments almost all year round, or at least start earlier each season, usually with salad crops (Perez – Vazquez, 2000). Generally there is a lack of practical information on crop species and variety choice for allotments and how they are liable to perform in urban conditions, i. e. higher temperatures, more shading, and variable soil factors such as fertility, compaction and the presence of some soil contaminants. An example of the range of crop species and varieties chosen is shown for one site in Table 20.1.
The yields of crops grown on allotments tend to vary and even more so for smaller plots of land close to houses (Perez-Vazquez, 2000). This variability is thought to be due to the lack of high yield as a priority, with many people growing such crops for recreational reasons (Gilber, 1989; Perez – Vazquez, 2000). Often, an allotment with a diverse array of small areas of vegetable and fruit species will tend to give lower yields per species than one where a smaller range of species are grown but on a larger scale. For example, potatoes are sometimes grown as a major crop in well-organised rows (giving higher yields) or occasionally as a recreational crop in just one or two short rows (giving lower yields). Allotment holders also tend to choose a relatively wide range of crop varieties (Gilber, 1989; Radice, 1997). Such diversity can be due to social factors such as family size, food preferences, and level of commitment (Perez-Vazquez, 2000). Thus, one urban allotment plot may show relatively large yield variation compared with a rural equivalent. One example for an urban allotment plot is shown in Table 20.1.
Figure 20.6 An example of crops growth in sunken pots to make the best use of applied water.
The irrigation of UPA in Britain depends mainly upon harvested rainwater (from the roofs of sheds into containers) and also mains supplies. The application of irrigation water can range from the use of hosepipes, to sprinklers, to hydroponic production systems. At almost every allotment site in Britain there is a water supply and water tanks are eventually provided. Whilst there is normally free access to this water, only watering cans may be used: the use of hose pipes is restricted or even prohibited in most allotments sites, though this does vary, see http://www. sags. org. uk/MerlinTrustReport. php4/ index. php, or http://www. inthelimelight. co. uk/localgov/ allotments/crops_water. html. Carpets, horse manure and mulches are used to retain soil water and suppress weeds. Pots may be buried in the soil to allow water to be retained more effectively in the vicinity of plant roots. Watering is usually difficult in summer time, especially for the elderly and less fit, due to the prohibition on use of hose pipes.