What to do with my lawn?
I have been fertilizing my lawn and treating moss with relative success for several years. Last summer I did minimal watering in the spring and did not water during the summer. By winter my lawn looked as though it was 90% dead. This spring I have only small patches of lawn with tons of weeds, moss and other growths I cannot identify. I am not sure if it is time to re-seed or re-sod or get a soil sample test or? Can a Master Gardener help me with this?
Unfortunately, it turned out to be a bad year not to water, although I realize you probably stopped watering because of a water shortage. I am seeing a lot more lawn damage in Oregon this year because of the lack of winter and spring rains coupled with our normal dry summers. The dry period was simply too long for a lot grasses to survive.
Resodding or reseeding can both work. Resodding gives you an instant result, but a higher cost. To reseed, you can either do a renovation which means kill the grass with glyphosate (e.g. Roundup), remove the dead grass with a dethatcher and seed into the exposed soil or a complete overhaul. Doing only a renovation avoids removing the sod, retilling, rolling to refirm the surface, and regrading. If your lawn needs to be regraded (i.e. the soil is uneven), a complete overhaul, will be your only choice.
Soil tests cost about $12 (A&L Western Labs is one example) which I would recommend having done just so you have the information, but your soil status is likely not the cause of your problems. Clay soils in western Oregon are, in most cases, fine (albeit wet and soft in the winter) for growing grass.
Sometimes I think we have gotten so environmentally conscious that we forget the basics: all plants need water and do much better with some fertilizer. With lawns, even if you do not plan to water your lawn regularly in the summer, it is best to give them a good soak at least once a month (every two to three weeks is probably better) to keep the crowns alive, else you end up with a lot of weeds. So you don't water, you end up applying a lot more herbicides to control the weeds.