I am flying from the US in May and I have a golfing size umbrella as a souvenir which I want to bring back but I already have 2 luggages and can't bring the umbrella as a carry on for safety reasons. Will they allow it be checked it in?
The size should be ok. It might end up as an oversize luggage which means that you'll potentially have to pay extra money for it.
Then with Qatar Airways, you have the right to check in 2 pieces in First and Business class and one piece in Economy.
Details here : http://www.qatarairways.com/us/en/baggage.page
You can also purchase additional baggage allowance. This way, you can check in your umbrella in addition to 1 or 2 pieces already included have by default.
It is likely that the airline would refuse to carry such an item as checked baggage due to the chances of it getting lost/damaged in the baggage handling system at the airport.