Originally Posted by Smallaxe
What else would add mass to the topsoil that would aid in the water soaking in???
Granular wetting agent followed by water
5% OM is what is commonly recognized as adequate in good soil mixes; also a number you don't want to surpass by much. Sometimes we add 100% OM to get to that number. I worked an entire growing season with my soil and compost provider and a soil testing lab to come up with a sand-compost topdressing mix that is suitable for most of my fields. Initially the supplier got kind of a laugh out of it as most folks around here just want "a load of black dirt." Once they saw the first series of lab results and the adjustments that were being recommended it became a matter of pride for them to hit my ranges. They have been making it for me now for almost ten years and it has been very dependale. I have shown them lots of before, during, and after photos. They are now recommending and providing this mix to others.
It's difficult to get any of it into the root zone unless you're starting from scratch and amending the soil. Otherwise several years of aerating followed by topdressing can make a difference. Around here not many homeowners would pay to see that through. If I have to turn a stand around and there are not any huge grading problems, I prefer to killl, slit seed, and topdress. There have been a few I have torn into, though, and I mean deep: 14-18". I have incorporated as much as 100 cubic yards of sand into a baseball infield (elevation needed help too) that had too much silt and OM. And I have tilled OM and soil into sandy fields.
Annual ryes have come a long way from the forage and paddock types like 'Gulf' to turf types such as 'Pantera.' You're still well advised to whisper if you want to mention annual rye in cool season turf. I sought opinions on using it from everyone from Riggle (thank you) to a golf course superintendent in Georgia. My sales rep liked it.The company had research on germination under traffic, such as on the football field where I used it as part of the overall mx. A couple colleges on the west sie of MI are using it on their athletic fields. In the end, I took a chance and have been pleased with the results. It was 20-25% of the overall mix. I am somewhat apprehensive about what the transition may look like but I know now that it's not going to occur in-season so it should be fine. There is also the argument that annual ryes just take food and water the permanent grass could be using. It was a matter of quick establishment and color under a lot of stress.
Axe, I'd say give it a try carefully - and I am sure I am in the minority, but I have just done it with good results. Do it as part of a mix though IMHO. I don't know that there will be quite as much benefit happening underground as you expect. You may need to regularly core aerate too.