Adjacency bonus provides benefits to land owners who own all of at least a 3x3 plot. this benefit goes to the dead-centre land of the group of plots.
Here’re some points to note:
in a 3x3 land, the height and depth of the centre plot is increased by 1.
Parts of a 3x3 plot can be factored into the adjacency of other plots, to offer more benefits to more plots. for example, in a 5x5 plot (that’s all owned by the same person), the rows can be combined to produce 9 different 3x3 plots. therefore, all the 9 centred plots in a 5x5 plot will benefit from the adjacency bonus.