What has been said about the guaranteed analysis is absolutely correct. However, several points need to be emphasized. If you only apply Ammonium Nitrate, you will only be adding Nitrogen. That only addresses the top growth. The other ingredients are there for a purpose. P and K add nutrients that are needed for root and stem growth and to some extent the sexual cycle.
As long as you apply Nitrogen and water every other day, you will have a great looking lawn. Then when you happen to go to the lake for a week and no one cares for your lawn, you will come back to a wilted brown lawn.
I would suggest that you go to the Scotts site. Determine the ratio for your area and then go to the feed store or Wal-Mart and buy the cheapest fertilizer you can find in the ratios recommended for your area. Why not just buy Scott's?
The answer is that the ratio on a bag of fertilizer is a guarnatee of the amounts of available NPK and all fertilizers with a guaranteed analysis are the same with one exception.
Available Nitrogen is delivered in one of two forms. Water soluble and water insoluble. The difference is found in the rate at which the Nitrogen becomes available after you water. The Water soluble is available nearly instantly and the insoluble is available over a longer period of time. Keep in mind that the available Nitrogen in a 10% Water insoluble fertilizer is guaranteed to be no more than the Nitrogen available in a 10% water soluble fertilizer. The only difference is the insoluble releases Nitrogen over a longer period of time. The caveat is that you will pay a BIG premium for the water insoluble Nitrogen. Scotts uses the water insoluble type of Nitrogen. That is the reason it is so much more expensive than the others. In reality, the insoluble type will only extend the Nitrogen availablity a few days longer than the soluble type. Ergo, find out what ratios are recommended in your area and get the cheapest fertilizer with the recommended analysis and apply it to your lawn.
Regarding preemergent fertilizers: They are nearly all worthless. It might be the time to apply pre emergent weed killers now in Minnesota, but in Texas, you should have had your pre emergent weed killers out by late January or at least February. Applying pre emergent weed killer at this time of year in my area is a waste of time and money. In addition, always, always buy fertilizer WITHOUT any weed killer mixed in. You need to fertilize on a particular schedule and you need to apply pre emergent weed killers...which is normally what is contained in bag fertilizer...at different times. Pre emergent weed killers mean that they must be applied before the plant emerges from the seed. The little plant emerges from the seed long before you ever see the first signs of green in your lawn in the spring. By the time you see green, the time is way past to use pre emergent weed killers. At that time you need to know what type of weed you are trying to kill and what type of grass you want to save. You will have to use some other type of weed killer, pre emergent is worthless once the plant has broken the seed cover.
At the very least, if you only want to fertilize and don't want to test, just buy the cheapest bagged fertilizer with a balanced ratio you can find. 13-13-13 or anything other than ammonium nitrate. I tried to buy bagged ammonium nitrate last year. It seems that after the Oklahoma City bombings, it is illegal to buy Ammonium Nitrate by the bag.
Now....lets talk about water, shade, types of grass, etc??????
Arli