William Taft actually said...
We must, therefore, if we would still retain agricultural control of the world, take some steps to avail ourselves of those great stretches of what seem now to be arid and desert lands, but which, by the application of water, when the water is properly administered, may yield a production marvellous to behold.
Context
Address at a Banquet Tendered by Citizens of San Francisco at the Hotel Fairmont
10/04/1909