Dog marking his territory.

My four year old castrated male husky has started a new habit, spraying up against my kitchen table! He is house trained and is always let out to run around and do his business regularly. His is also walked once a day sometimes twice if I'm not working. In fact he spends most of the day out and about in the dog run with my other dog. I bring him in when I'm at home and he sleeps in the kitchen at night. I know this is a behavioural problem but I don't know of what sort or how to solve it. Leaving him out permenently is not an option. Anyone experience the same or have any ideas? It would be greatly appreciated! Thanks.