Lawn Dry Patches
During last summer after a very dry spring, many lawns were blighted by dry patches where the grass plants appeared to have died out. We looked at many areas where overseeding had been tried but to no effect.
The main reason for these patches was a phenomenon known as “dry patch”. Dry patches are partly caused by the presence of waxy resins which are caused by naturally occurring soil fungi (basidiomytes). These resins bind the soil particles together causing the soil to repel water and become hydrophobic meaning that water cannot penetrate. In a more normal year, these resins are naturally flushed through by rain water. However, we have had several warm winters of late which have allowed more fungal activity and the generally dry conditions have led to an increased buildup which seemed to be higher in soils that contain an element of silt particles.
The very dry April followed by a hot spell caused a bit of a perfect storm and dry patches began to appear where the soil became so hard and dry, roots were not able to penetrate or function. When it did rain, the water ran off these areas into the surrounding soil that was unaffected. Once the soil becomes "super dry". It is difficult for it to rehydrate without some help. The picture shows the difference in two patches of soil next to each other late last autumn. The area too the right is still very dry. In many cases, it was easy to see the white mycelium of the fungi.
Remedial action is centred around physically breaking up the soil using very thin (less than 3mm) blades which penetrate the soil to depth. This allows us then to apply soil wetting agents which also contain detergents which will help break up the wax and allow water to penetrate. We also apply fungicides to help reduce the fungal activity.
These soil acting basidiomytes are the same type of fungi that cause fairy rings and again, the conditions last year made these much more apparent, (even during a test match at Lords).
One of the other issues that helps this problem take hold is too much thatch in the grass so we can also scarify gently to reduce this issue.
As we move into the spring, we want to make sure that we look after the soil under your lawn moving forwards and on the soils that were affected in the main last year (parts of St.Albans, Welwyn, WGC, Hitchin and parts of West Essex). We will be suggesting that we aerate the soil as it drys moving into the spring and applying appropriate chemistry.