Q & A WITH PAMELA SHERRATT

What are your thoughts on leaving the thatch after slice seeding ? In the past we have lightly raked it up , but it is time-consuming . I see other companies leaving it behind . Will it adversely affect seed germination ?

– Matt M .

On a native soil field , I don ’ t think there would be any detrimental effect to leaving the thatch / leaf debris on the surface , other than it looks unsightly for a few days . In fact , it might act as a mulch , keeping moisture locked in and preventing the seed from moving during a wind or rainstorm . If the debris layer is too thick though , it could adversely affect athlete and ball performance , and might impede light penetration .

It would not be acceptable to leave any kind of thatch debris on a sand-based field . Removing organic material from a sand-based surface is one of the key elements to sand-based field management , because the rate of organic matter accumulation exceeds the rate at which soil organisms can break it down . Also , the field surface needs to be free-draining and provide acceptable footing / traction for the athlete . Organic material left on the sand surface can produce a slick layer of biofilm or algae that creates a wet , slippery playing surface . Dr . Dave Minner coined the phrase “ snot layer ” to describe this phenomenon . When I wrote my thesis on organic matter control on hybrid turf systems , I preferred the term “ hydrated clipping layer ,” but I think Dave ’ s term captures the essence of it better .

Addressing this question from an agronomic standpoint , let ’ s look at what thatch is . Thatch is an organic layer composed of old grass roots , crowns , rhizomes and stolons that sit atop the soil surface . Leaf clippings do not contribute to thatch as they are 80 % water and are broken down very quickly . Thatch takes longer to break down because it contains more organic carbon . When the lower layer of thatch ( nearer to the soil surface ) mixes with soil it forms a layer referred to as the “ mat ” layer . Mat is in a more advanced stage of decomposition than thatch , and retains more water and nutrients than thatch .

The rate of thatch accumulation in cool-season grasses varies by grass species . Creeping bentgrass produces more thatch than Kentucky bluegrass , which produces more than fine fescues > perennial ryegrass > tall fescue . Thatch buildup is also more likely to occur on compacted soils and low-traffic / impact areas such as endzones and outfields .

Both thatch and mat provide a cushion that creates a softer landing area for athletes . The thatch / mat layer also insulates the ground during cold weather and helps to retain moisture . However , a thatch layer greater than 1 / 2 inch can become soft and spongy and inhibit the infiltration of water , air and fertilizer into the underlying rootzone . Thatch can also attract insects such as cinch bugs , sod webworms and grubs , which in turn attracts skunks , racoons and crows . Because thatch is rich in organic carbon , it can also inhibit the movement of pesticides into the underlying soil . Pesticide sorption by organic matter , and degradation of the pesticide by soil microbial populations in that organic matter , can have major effects on the efficacy of a pesticide product . Thatch will increase the pesticide degradation rate and reduce movement of immobile and moderately mobile pesticides . It may not have as much impact on more mobile pesticides . Thus , pesticides that need to be watered-in ( such as insecticides ) may be severely impeded by a thatch layer . Thatch management is best performed by core aeration and either redistribution of soil cores ( native fields ) or topdressing ( sand fields ). This process dilutes the thatch with rootzone material and promotes biological degradation . Dethatching , scarifying or verticutting are mechanical removal practices that are commonplace , but they can cause stress to the turf in hot , dry weather , and they result in debris that needs removed . If the thatch layer is greater than 1 inch thick , a more aggressive coring , topdressing and dethatching program needs to be in place . SFM

Pamela Sherratt Sports turf extension specialist The Ohio State University

Questions ? Send them to Pamela Sherratt at 202D Kottman Hall , 2001 Coffey Road , Columbus , OH 43210 or sherratt . 1 @ osu . edu

Or send your question to Dr . Grady Miller , North Carolina State University , Box 7620 , Raleigh , NC 27695-7620 , or grady _ miller @ ncsu . edu

50 SportsField Management | October 2023 sportsfieldmanagementonline . com