Spreading vanes are wearing parts. For spreading vanes we use manganese steel simply because it has some clear advantages. The temper which is three times compared to stainless steel clearly indicates that it is the right choice for wearing parts. Additionally manganese steel does not burst from hammering and knocks.
Despite the ideal properties of manganese steel there will be wearing depending on fertiliser type. The largest effect is seen in connection with spreading of mineral-bearing fertilisers, where the wearing often is factor 3 or more.