Clematis - Fertilizer Requirements

My question is how to fertilize young (2 yr) Group 1 clematis.

We have four that we will plant in the next two days. I've already read about soil conditions, planting depth, top dressing and watering and I am clear about those requirements. But when I look up what fertilizer to buy there appears to be varying opinions and even contradictory information.

I live in Switzerland and some of the feeding suggestions I have seen on this board, e.g., pelleted chicken manure, FBB and others are simply not available here or at least I haven't found them. What I really would like advice on is:

1. The NPK for Sping, Summer and Autumn.

2. Liquid vs. pellets vs slow release
3. How often to fertilize with each of these options. 

4. Fertilize now or wait a year.

The clematis will be planted along a north facing wall that receives sun in the late Spring and Summer for about 7 hours per day. 

The soil is slightly alkaline.

Hardiness zone: 8a

I welcome all suggestions.