Complex sentence: The Stolypin reform created a new class of landowners who were allowed to acquire for credit a plot of land from the large estate owners, and the credit (a kind of mortgage loan) was to be repaid from farm work.
Split into simpler sentences: The Stolypin reform created a new class of landowners, who were allowed to acquire for credit a plot of land from the large estate owners. They were to repay the credit (a kind of mortgage loan) from their farm work.