Italian to English Law/Patents Certificates, Diplomas, Licenses, CVs Civil registration certificate

I am confused about what this phrase means in the context. I would normally see this as "Employment contract for employees and letting of farm lands" or something on those lines. However, I have no idea why this would be at the bottom of a certificate of family registration from the "L'Ufficiale Dello Stato Civile". Could it be that the person's employment as a farmer has exempt him from paying stamp duty?

The whole paragraph reads:

"Si rilascia in carta libera. Contratti di lavoro e impieghi locazione fondi rustici: libretti colonici (ART.25 TAB.B DPR 642/1972) - Il presente certificato non puo essere prodotto... " etc