The state treasurer shall hold all state moneys, all deposits thereof, time as well as demand, and all obligations of the United States government in which such moneys are placed for the benefit of the respective funds to which they belong and disburse the same as authorized by law. Unless otherwise provided by law, all yield, interest, income, increment, or gain received from the time deposit of state moneys or their investment in obligations of the United States government shall be credited by the state treasurer to the general revenue.