Is there a soap that will take out the brown spot in the lawn?

Answer 1

In the original answer, the post was partially correct. *IF* the plant is dead, soap will not help. However, dish detergent and other soaps act as a penetrant or "Soil Surfactant". What this means is that the detergent acts to lower the surface tension or cohesive properties of water. If you've ever seen the trick where water is dripped on top of a quarter unti it forms a "bubble"; this is an example of the surface tension of water. Water has the ability to "roll" off of a hydrophobic surface, until it finds a more hydrophillic one (water hating, and water loving respectively).

When you add a detergent to the water, it breaks down the chemical cohesion between the water molecules and allows it to more easily be absorbed into a hydrophobic soil.

So to answer your original question; If the "brown spot in the lawn" is caused by dry soil which will not take in water, then a 1% solution of liquid dish soap in water should be enough to saturate the soil. If the turf has been killed off by the drought, however, then it will not come back until new, living grass plants are introduced, either by the surrounding turf, seed, or sod.

There is no known soap that will bring dead plant matter back to life.