Reduced volatility of urea fertilizers are prepared in accordance with the present invention by first preparing an N-(n-butyl)-thiophosphoric triamide (NBPT) solution by dissolving NBPT in a mixture of an amino alcohol having the formula 1—(H)x—N—((CH2)m—OH)n where m is 1-3, x is 0 or 1, and n is 2 when x is 1 and 3 when x is 0: or the formula 2—(H)y—N—((CH2)—CHOH—CH3)z such that the length of the carbon chain where the secondary hydroxyl group is located is 3, y is 0 or 1, and z is 2 when y is 1 and 3 when y is 0, and a carboxylic acid having 6 or fewer carbon atoms. The solution is then combining with a urea fertilizer in granular or liquid form.
