I now keep white sidewalk chalk handy in my laundry room. While watching my youngest son at football practice, I was fortunate to meet the mother of one his team mates. Having been responsible for washing the football pants of her son's entire team while living in Western Canada, she learned a tip from another about the usefulness of white chalk in removing grass and dirt stains from football pants. Now, before I wash the pants, I rub the stains vigorously with white sidewalk chalk. Ordinary chalk works okay as well, but is much thinner and breaks more easily making it harder to use. If the stains are deep, I also use Spray and Wash on top of the chalk and then soak for a couple of hours. Later, I wash as usual. Even in cold water wash, most or all of the stains are removed and the pants are much whiter. This method works well on other whites as well!
There are two products I have always kept in my house and used often but for reasons that differ from their predominant use now. Vinegar and most recently white sidewalk chalk have become essential staples in my cleaning arsenal.