Crop diversity and plant–plant interactions in urban allotment gardens

Abstract

Allotment food gardens represent important sources of food security for urban residents. Since urban gardeners rarely receive formal agricultural education and have extremely limited space, they may be relying on readily available gardening advice (e.g., seed packet instructions), inventing cultural strategies that consider inter-specific competitive dynamics, or making poor planting decisions. Knowledge of garden crop diversity and planting arrangements can aid in designing strategies for productive urban gardens and food systems. We surveyed 96 individual plots in 10 allotment gardens in the Toronto region, assessed crop diversity within gardens and recorded planting practices used by urban gardeners by measuring the proximity of individual plants relative to similar or different crop species. We also compared planting densities used by urban gardeners with those recommended by major seed distributers. Collectively, Toronto urban agriculture contributes substantially to urban plant diversity (108 crops), but each plot tends to be relatively depauperate. Carrots and lettuce were three to five times more likely to be planted in clusters than intermingled with other crops (P < 0.05); whereas gardeners did not appear to use consistent planting arrangements for tomatoes or zucchini. Gardeners tended to plant tomatoes and zucchini 56–62.5% more densely than recommended by seed distributers (P < 0.001), whereas they planted 147 times fewer carrots in a given area than recommended (P < 0.05). Furthermore, neither crop planting density nor crop diversity changed with plot size. The planting arrangements we have documented suggest gardeners using allotment plots attempt plant densely in extremely limited space, and are employing cultural strategies that intensify competitive dynamics within gardens. Future research should assess the absolute and relative effect of altered cultural practices on yield, such that any modifications can be prioritized by their impact on yield.

Food production and resource use of urban farms and gardens: a five-country study

“…Studies that employ citizen science frequently characterize systems qualitatively, surveying crop choices and cultivation practices, but often stop short of measuring yields and farming inputs (Algert et al 2014 ; Woods et al 2016 ; Kirkpatrick and Davison 2018 ). When such data are collected, datasets are usually limited to a relatively small number of case studies (10-35), covering one type of UA in one location (Algert et al 2014 ; Pourias et al 2015 ; McDougall et al 2019 ; Wielemaker et al 2019 ; Sovová and Veen 2020 ; Csortan et al 2020 ).…”

The Role of Urban Agriculture as a Nature-Based Solution: A Review for Developing a Systemic Assessment Framework

“…The majority of the studies deal with the mapping and assessing of multiple ecosystem services provided by different kinds of UPA e.g., [60][61][62]. However, some studies focus solely on one benefit, mostly on biodiversity (8 papers, e.g., [63][64][65], followed by regulating services (7 papers) mainly related to run-off mitigation [66,67], maintenance of soil quality [68,69], microclimate regulation [70], and pollination [71]. The focus of the studies dealing with ecosystem services and biodiversity is clearly on community gardens (14 papers, e.g., [60,61,72], followed by private/home food gardens (6 papers, e.g., [73][74][75] and allotment gardens (5 papers, e.g., [60,68,76]).…”

“…For analyzing enabling factors of UPA stakeholder interviews [111] and planning analysis can be conducted [110]. To visualize multiple ecosystems services provided by UPA, remote sensing [165], models such as inVest analyzing the pollination potentials [75], plant inventories and regression modelling [64], or interviews with gardeners [61] can be conducted, to name only a few methods. For the integrative assessment an inter-and transdisciplinary team is recommended.…”

Modeling the Potential Productivity of Urban Agriculture and Its Impacts on Soil Quality Through Experimental Research on Scale-Appropriate Systems

“…Plots are small, and gardeners and farmers may be reluctant or unable to leave areas fallow to allow the soil to recover from intensive production, to rotate crops to break pest cycles, or to plant cover crops to reduce soil erosion and to improve soil quality. In home and community gardens, crops may be grown in mixed polycultures, with two or more crops growing in intimate association (Airriess and Clawson, 1994;Woods et al, 2016;Taylor et al, 2017). Even if crops are grown in single-species rows or blocks, plots represent polycultures compared to the scale of commercial field production, with many of the potential advantages and disadvantages of intercropping, including increased or decreased yields, reduced pest pressure, high knowledge demand, and increased labor (Lithourgidis et al, 2011;Yu et al, 2015).…”