Over time, bent grass putting surfaces develop an organic layer. Before we go any further, lets define an organic layer versus a thatch layer. Although a thatch layer can become quite deep, say 1.5-2", thatch on a well managed surface is much more shallow. Thatch is indigestible plant parts composed of lignin. Thatch is different from an organic layer because it is not decomposed easily by microbes in the soil. Frequent topdressing, core aerifying and verti-cutting are great tools to reduce thatch. An organic layer is generally deeper than thatch and it is composed of digestible plant parts, minerals and humus. Although there are many benefits to a good organic layer (mineralization, crown protection, etc.) it can become a barrier to gas exchange, oxygen diffusion and it can become easily saturated leading to anaerobic soil conditions. Topdressing greens is a great way to mitigate an over-accumulation of organic material, but topdressing is mostly confined to the upper surface of the root-zone. In fact, sporadic topdressing can lead to a layering effect that sometimes resembles tiramisu.
Introduce dry-ject. Dry-ject is a process where sand can be injected into the root zone on 2"x3" centers. The dry-ject operator can target a specific depth depending on the organic layer in question, Dry-ject deposits a small pocket of sand at each entry point. This pocket of sand allows the grass a fresh, aerobic opening to drive roots and this pocket also allows for great water infiltration. The good news is that all of the benefits of the organic layer are left in tact while the physical properties of sand are introduced to an otherwise stagnant medium. In fact, the organic material is pushed further into the profile. Over time, that organic is more easily diluted and the minerals remain in the root-zone. Dry-ject allows the superintendent to enjoy the best of both worlds.