Fertilizer for Grapes

[marlingardener]

Our Mars grapevine is growing like mad, and setting on a lot of grapes. Should I remove some of the bunches (they are very tiny yet) or let them all grow?
Also, I looked up fertilizer for grapes and found that a high nitrogen fertilizer was recommended. We have hens, who put out lots of high-nitrogen daily! I have compost with the ladies' output incorporated and plan to put some around the base of the vine.
My question is, how much of this high-nitrogen compost should I use for a vine that is about 10' long and H-shaped?

 

[headfullofbees]

The length of the vine is irrelevant; it's about soil levels.
If it's too "hot" it will burn the roots.
1 bucketful will be plenty.