The allotment system is almost self explanatory. You are "allotted" some land on which to grow. Here's an interesting link to their history.
http://www.allotment.org.uk/articles/Allotment-History.php
Anyway, as an ex-allotmenteer, I am profoundly shocked by the decisions of Dave's allotment society. In my opinion it's absolutely typical of the invasion of the allotment system by the middle classes. In the "good old days", you got in touch with the local council - or whoever it was who owned the land that had been dedicated to allotments, and asked them of you could rent a "lottie". Depending upon the law of supply and demand, you might get one right away, or go on the list to get one as and when one became available. As far as the council was concerned, what you did with the land was more or less up to you as long as you were using it and not being a nuisance to the others.
Because - in general - people without a lot of spare money were those to whom some land to grow on was most useful, and because - in general, manual labour etc is less well paid than "white collar" work, allotments were most often in the past used by people from the least well-off. They tended to be people who used to "live and let live". and they would have never dreamed of telling others what to do. They might use their "lotties" to grow prize winning begonias, or magnificent leeks or marrows, but the very concept of imposing "90%" cultivation would have been completely foreign to them. Partly because the traditional crop rotation - to which I ALWAYS adhered, puts aside one year in three or four when the land was left fallow or planted with a green manure such as alfalfa or clover.