In India, majority of the farming is still done with old traditional technology. -> Obsolete and worn put equipment, old ideologies, lesser mechanization, etc. all reduces agricultural productivity.
Farmers also use traditional seeds instead of modern hybrid seeds which can give higher productivity.
Many farmers use traditional manure such as cow dung instead of chemical fertilizers. This also reduces the productivity.
Indian farmers do not use pesticides in sufficient quantity. As a result, the crops catch disease and the productivity suffers.