When you come to the land

The system of sheviit and shemitta revolve around the question of property rights and property allotments. 

When the Children of Israel come to the Land of Israel several things happen: 

• they desist from their nomadic lives, and their subsistence on mannah is suspended, which mannah enabled such a national entity to live in the desert (and which subsistence was governed not by the laws of sheviit and shemitta but by the laws of the shabbos day); 
• the land of Israel is allotted to the people (but only subject to the choq of God's retaining certain prerogatives over how the land is used); 
• the people of Israel begin to work the land in agricultural settlements, and, correspondingly, the distribution of wealth and income becomes subject to the vagaries of fortune; 
• the possibility of the land's devisement outside the original allotment, with subsequent political ramifications about the distribution of land as between the several tribal units becomes a problem (here we see the sovereignty over the land was allotted to the tribes but only through the individual persons of the tribal populations and not officially to the tribe as a legal person in its own right); 
• the possibility of a person's loss of autonomy on account of severe reversals of fortune (along with a corresponding extension of property rights to include the transfer of real property such as land, and the transfer of personal property such as indentured servitude); 
• debts become a problem as the persistence of property claims over too long a period of time; 
• poverty becomes a problem as the persistence of property claims over too broad a cross-section of the population. 

The laws of sheviit and shemitta return the laws of property from the tribal, nomadic forms that shaped them while the nation was encamped as a single unity within a single geographic perimeter. We can see a subtle hint to this effect by the location of the yovel year as beginning at the end of Yom haKippurim. Convention thinks that it has to do with the Yom. In fact, it has to do with the festival of Succoth. The paschal lamb was set aside on the tenth of the month, and so is the return to a more full-bodied set of encamped and nomadic rules as the succah is the re-enactment of that encampment by building a corral around the geographic limits of the nation (and not a hut).