https://www.theguardian.com/environment/2021/dec/15/city-allotments-could-be-as-productive-as-conventional-farms-research-finds
Well, yes the allotment is productive but there is always the hungry gap (which would be very hungry if I couldn't suplement from the shops or market). But it reflects substantial input of time which isn't possible on an agricultural level.
Productivity
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