Grass plants even in the healthiest and well maintained lawns die to be replaced by new grass plants. The dead stalks lie with other vegetable debris on the soil surface forming a layer of dead organic material called thatch.
A small amount of thatch on the soil surface is acceptable as it will gradually decompose; its nutrients will be digested and broken down by bacteria naturally present in the soil who return it to the soil where they will be taken in as nutrients(food) by the new grass plants.
If the bacteria in the soil cannot digest the thatch on the soil surface fast enough an excess builds up and acts like blotting paper blocking the flow of moisture and air to the soil and grass roots.
In dry periods thatch holds much needed water near the surface preventing moisture getting to the roots. During Autumn and Winter in wetter periods the surface thatch remains damp and humid creating ideal conditions for moss and many grass & turf diseases to flourish.
If your lawn feels spongy when you walk across it you either have thatch or have been using fertilisers with excessive cheap nitrogen that have encouraged too much surge growth in the grass. Too much top growth is not desirable and will cause problems. If your lawn is thick and spongy your lawn should be scarified. Lawn and Weed Expert will check your lawns each time we visit to assess if scarifying is required.