Question
We fertilized our pastures about 3 weeks ago.  In the last couple of days the leaf on all the grass has died and the stem is standing.  We have had rain, not alot, but have already made two cuts of grass throughout the drought, so why is this happening now.  We live north of Houston and our ground is almost alway yet, except this year.

Answer
You fertilizes three weeks ago and the grass blades have died. The area my have had a 'drought'. You do not say whether you irrigate the lawn or pastures.
The 'worst scene scenario' is that the grass was suffering moisture stress and you applied fertilizer. There was neither rain nor irrigation and you mowed the area twice since applying the fertilizer.
The grass needs to leaf out urgently. Water it to wet the top six inches of the soil and keep at it until the grass has filled in to your satisfaction.
Other causes might be that the fertilizer was over-applied, that it may have been a Weed and Feed combination or contaminated.