A guy by the name of Oliver Poitrey has created a free and open source Safari plug-in that merges the location bar and search bar into a single what he called an Omnibar. The Omnibar mimics the same bar as found in Chrome browser.
Just type on the bar web address or search term, Omnibar is able to detect if it is a URL or launch the search engine for the search term. You can define the search engine to use by holding Option key while clicking on the bar. Typing “?” to begin your input will launch a search. Typing “w” to begin your input will search for Wikipedia.