About this time, your lawn is taking a rest from its semi-annual job of growing fast and looking green. Most types of grass, especially in the temperate zones that make up most of the US go through a period of dormancy in the summer. This would be a good time to start thinking about switching to organic lawn care if you aren't practicing it yet. There are a lot of advantages to growing your lawn without using inorganic chemical fertilizers and weed killers. If you are already an organic lawn-care aficionado, that's great. When the summer is over you've got some work to do.
First of all, there's no time like the present to have your soil tested. There's no substitute to knowing what you are dealing with scientifically. The three major nutrients that fertilizers contain are nitrogen, phosphorus and potassium. Fertilizers are formulated with different amounts of these three essential fertilizing elements, as spelled out on every fertilizer label. You have to pick out a fertilizer that matches the chemical profile of your soil. In fall, it's important to increase the amount of nitrogen to facilitate root growth, which is necessary for successful over-wintering. There are a wide range of natural materials from which organic fertilizers can be derived, such as bone meal, blood meal, fish meal, feather meal, enzyme digested proteins, treated sewage, seaweed, worm castings, guano, and a many others. Organic fertilizers, because they release their nutrients more slowly, promote worms and beneficial bacteria, and add humus to the soil. This eventually helps to break up dense soils such as clay and sandy soil and allow them to retain moisture.
Organic fertilizers are a bit more expensive than inorganic ones, but in the end they will save you money because they are safer and easier for the lawn to absorb properly, you have to use less fertilizer to get the same amount of nutrition to your grass, and using organic fertilizer will decrease and eventually eliminate the need for using herbicides to control weeds. Until your lawn is established and healthy enough to fight off weeds on its own, you may have to use some weed control products. Luckily, there are some organic ones on the market that are safe to use. A good homemade organic spot weeder is a mixture of white vinegar, water, and dishwashing soap in a 4 to 2 to 1 part dilution.
Liquid seaweed is another fertilizer that you ought to consider using. Some experts advocate giving the lawn a seaweed bath every month. Seaweed gives the lawn a shot of trace elements that also promote root growth and disease resistance. Spray liquid seaweed according to directions when the ground is moist. You will need to spread lime to get the pH to the proper range which is somewhere between 6.0 and 7.0. Use about 30 pounds of palletized limestone per 1000 SF. If your test shows high magnesium content in the soil, substitute aragonite, which is calcium chloride derived from ground seashells, or calcium limestone flour, which is finely ground mineral calcium chloride. The advantage of aragonite is that it will also help keep squirrels and moles away from your flowerbeds.
Spread compost or composted manure on the lawn at a rate of 100 pounds per 1000 square feet. Late summer or early fall is a good time to overseed. Rough up any bare spots and add topsoil or peat and seed them heavily, then very lightly over seed the entire lawn.