Recover from summer and gear up for fall
What is thatch, and why can it have a negative effect on water quality?
Thatch is the layer of dead and decomposing plant tissue that forms above the soil. A thin layer of thatch is beneficial to lawns. It will protect the crown of the plants and reduce soil compaction. Heavy thatch buildup results when the production of plant tissue exceeds the decomposition rate and can be encouraged by excessive growth in the spring. Fertilizers and nutrients are ineffective when water and materials cannot penetrate the thatch layer. Localized dry spots appear when the thatch becomes water-repellant and runoff increases.

The plants respond with reduced root and shoot growth as well as reduced water and nutrient uptake.   As the turfgrass thins, the risk of surface runoff from bare areas increases. This is common on heavy clay soils or soils that receive traffic such as athletic fields.

What is core aeration, and how can it have a positive effect on water quality?
Core aeration, which should be done in late August, punches holes in the lawn and pulls out cores. The holes increase infiltration of water, nutrients, and air into the soil. Core aeration should be 
performed as temperatures cool and soil moisture is adequate. Allow cores to dry on the surface, then break up with a rake and distribute evenly over the lawn as a topdressing. Be careful not to move soil particles off site because they contain phosphorus, which is a leading threat to water quality in many parts of the country.

Improved infiltration

Turfgrass Growth

An average lawn can allow water to run off at about half a gallon per minute during peak rainfall. By comparison, 7.5 gallons of water may run off from lawns that are thinly seeded. If your lawn has large, bare areas, consider renovating or reseeding. August is the best time to start turf growth from seed.

Practices that promote deep rooting are beneficial at this time of year for food storage to get through winter, supply energy needed for spring greenup, and reduce production of clippings in spring.

August is a good time for

• Alleviating compaction and thatch problems before the fall surge of growth: Toward the end of the month temperatures become moderate, soil moisture is adequate, and the turfgrass begins to recuperate from the stress of summer and gear up for fall root growth.

• Mowing: Keep up with mowing as the grass recuperates from summer stress and begins active growth.

• Controlling broadleaf weeds: Consider a postemergence material in the second half of the month if needed. Hand weed for light invasions.

• Fertilizing: Wait until plant recovers from summer stress, usually by Labor Day.

• Scouting: The middle of the month is a good time to begin sampling 
  for grubs.