http://www.infoplease.com/encyclopedia/science/collective-farm-in-soviet-union.html is the most comprehensive of the sources I used to refresh my memory of my studies of Russian History; it doesn't discuss the size of harvests or the tendency of new Party Leaders to repeat the same mistakes of their predecessors, nor the widespread black markets that underpinned the Soviet economy. I will try to find the five or six textbooks I studied from, however.
The link doesn't support your claims. There was no "renewed collectivization effort" in the 1950s, what happened was that small kolkhozes were merged into big ones. And the increase in "private plots" is the increase of the size of personal gardens, basically -- don't think they can be properly called "privately held sections of farmland". People certainly used them to grow and partially sell produce, but everyone had to have a day job anyway. These private plots, as far as I know, always existed and post-WW2 only expanded. I ...
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.