the rotation isn't a problem - i dont have much space and wanted to do second sowings rather than having ground left empty - just wanted to know if i should have sown more of the same in the summer (spuds then spuds / peas then peas) or not

the bottom line seems to be that i shouldn't do it - but i could sow next year's crop early, which is more like the 3 year rotation becoming 18 months - replace spuds now with peas and when they're done in a couple of months, plant brassicas to overwinter and they'll be ready in spring

which means that bed will have had all 3 types in 18 months instead of 3 years .... which kind of defeats the 3 year rotation plan ..... and then i'd have to leave the beds empty for 18 months??

thing is, i'm sure i've read that some people sow peas where the current peas are growing, so that the new peas replace the old .... ?? and i don't want empty ground?
i'm getting more confused now ....