FERTILIZER BURN - SOMETHING THAT CAN BE AVOIDED
Fertilizer burn occurs every year to some extent.Experience has taught me that once the combined broadcast application of ammonia from urea and the salts of potash exceed 200lb/ acre on sandy loam soils fertilizer burn can become a reality.Once combined levels exceed 220lb/acre on sandy loams and soils remain dry for any extended period the severity of burn will increase.Over 240 lb/acre of the two combined and you're in for BIG TIME BURN.Add a liquid pop-up fertilizer to the mix and you are adding insult to injury.Even heavy manure applications on sandy soils can lead to fertilizer burn.The best way to confirm fertilizer burn from salts is to take cores of soil 2 inches deep right through plants suspected of burning from salt injury.
A simple laboratory test will corfirm your suspicions.

You can be 99.9% certain that fertilzer burn has occurred when you dig up plants like those shown on the right side of the above photo and you see NO RADICLES.
When radicles are missing or appear as blackened tips its a strong tell tale sign that they were burnt from too much ammonia and salt injury.

The surest means of avoiding fertilizer burn is to split your potash and N fertilizer applications.Of course you should never exceed 10 lb of N + K in a liquid pop-up on the seed and you should never exceed 70 lb of N + K in a 2 x 2 band.