FOUR GALLONS?? Yeah if I want to have a rain forest overnight maybe, LOL. I assume you are talking about 4 gallons of water with 3 oz of product then sure why not but a bit of an over kill on the water.
I have applied it at 3 oz per 1000 sq/ft with one gallon of water. If it is dry or not much rain (before or after treatment) I will water in or tell home owners (if no sprinklers) to water in 3-5 minutes to get product into the soil quicker.
Have had very good results and am very happy with the end results. After this last rainfall we got hammered with the grass really looks impressive and better then lawns I am not treating done by other companies. No idea what they are using but my clients are happy. Their happy, I am happy and money is better. Three things I look for when all is said and done.
I am sure you already know this but Sumagreen is a highly concentrated form of microbes. Right now I would not use more then 4 oz per 1000 sq/ft at once time. I have used with 3 oz by itself on several lawns and 2 oz with 1/8 fert on several to compare. Not the most scientific way but an affordable way for me. Yes i know every lawn is different but this works for me. I did not notice any real difference in the lawns as a whole but did notice better growth in the shade and under trees with the sumagreen compared to other years. Rainfall was probably less this year to boot.
I wish I did take a soil sample or two just for a reference to show my clients so maybe next year with a new client or two I will take some soil samples to show the OM difference. Again no scientist but everything above and below the ground looks good to me. I took a shovel and went to stick it in the ground about 2 weeks ago to see the roots and what I did notice was that the shovel went in the ground easier and deeper on the treated side better then the side I was not treating my lawn. This was my lawn which again is not the best test but what it did show me is that the compaction of the soil was broken up on the treated side of the yard.