not exactly my field and I hope that some colleagues come up with additional information, but here are some general information on the situation in Germany:
The "Sozialversicherung für Landwirtschaft, Forsten und Gartenbau (SVLFG)" replaced the former (independent) regional agricultural social insurance institutions with the start of 2013. The SVLFG is owned and run by the federal government and provides social insurance for agriculture, forestry and horticulture in the four areas : accident , pension, health and nursing care.
Membership in the social insurance is compulsory for owners of agricultural, horticultural and forestry enterprises. Exceptions are possible, but accepted criteria for an application for exception are quite limited (e.g. farm size below 0.25 ha, negligible profits from agriculture etc.).
Employees in agriculture are generally subject to social insurance (incl. unemployment insurance) , whereby the employer and the employee have to cover for (about) half of the contributions. Exceptions from certain parts of the social insurance (pension, nursing care, unemployment) and different schemes for contributions to the health insurance are possible for part-time employees.
In Macedonia, as farmers (unless registered as enterprise) are considered persons whose only source of income originates from agricultural activity and through this kind of activity they are obtaining their basic needs for their livelihood.
Until 31.12.2008, the former Law used to calculate the base for this kind of insurance upon cadastre income. Since that group of farmers were having quite small cadastre income since February 2008 an amendment was adopted by which the calculation level was accommodated according to this specific case. According to the new Law, the base for calculation for the "social insurance" is 20% of average salary in the Republic of Macedonia (the old Law used to calculate on 30%).
if you wan't information for Germany Peter Mehl ([email protected]) is one of the leading experts. He was also a good overview on the situation in France and I think also in Austria.