Both 10-10-10 and 13-13-13 fertilizers provide an equal ratio of nitrogen, phosphorus, and potassium. However, for Bermuda grass, it is best to choose a fertilizer with an emphasis on nitrogen and a reduced phosphorus level. Therefore, neither 10-10-10 nor 13-13-13 ratios are ideal for Bermuda grass. Instead, look for fertilizers with a higher nitrogen ratio and lower phosphorus content.