Temporary Employment for only 6 months. So on what basis we recruit them?

I am working as an HR in agriculture-based industry. June to December is the season for us. so that time we recruited some people for different locations based on our requirement. As of now, we showing them in off roll. They don't have any statutory benefits. What I am asking is if anything happens them in the field the company is responsible. so my management asks me to find out the solution for this.
1)If we take them in direct into on rolls then after December what should we do with them?
2)If we ask them to give a resignation for his job after the completion of 6 months work period?
Is there any alternative solution for this problem. one thing is clear we provide employment for them only 6 months. So on what basis we recruit them? Management is ready to pay them ESI & pf.

Seasonal workers are also permitted to get employed and make exit on completion of job ....... and they are also eligible to ESIC/EPF/PT/LWF

Dear Prasad,
I am constrained to state that certain modern management jargons with or without intentions behind them are very loosely employed now a days in the domain of HRM; "Off Roll Employee" is one among them referring to the indirect labor engaged by an organization generally through a third party. For the purpose of all statutory benefits other than permanency of employment, such employees become automatically covered by the provisions of every labor law for the simple reason of the application of the concept of vicarious liability thrust up on the employer for whom the services are rendered by such "Off Roll employees'..

Hi,
These employees can be taken of "Fixed Term Contract Basis " ie. their contract of employment can be only for the specified six months.
They should be covered under PF & ESI. Also they should be assured that in the next six months cycle they would be given preference.
Thank you,
Regards,
R. H. Kavarana