Answer: How aggravating! The fertilizer can eventually be leached by watering heavily and repeatedly, or you could try replacing the soil in those spots. Otherwise, time will eventually solve the problem.
When using a drop spreader, it is better to measure the amount of fertilizer you need to use for the square footage you have to cover, then set the spreader on a very light application, and then go over the area repeatedly at the light rate until the fertilizer is used up.
Be sure to follow the label instructions as to how much to use in total, because it is better to use the right amount or if anything, underfertilize than to overfertilize.
Also change your walking pattern (eg up and down and then back and forth and then diagonally both ways) as you go to avoid accidentally leaving any lines or skipping places.
By using a low rate and spreading in different patterns you will not overdose any particular area and you will still use the recommended amount of fertilizer. It takes a little bit longer, but it makes it nearly impossible to overdose any spots.
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