Lawn Care Experts

No Scorch Fertiliser

What is Grass Burn or Scorch?

You may have experienced or heard of fertiliser burn or scorch on the grass. The term is descriptive rather than scientific. Green or organic fertilisers, composts, mulches or manures are not considered to have scorch risk whereas manufactured, mineral or non-organic fertilisers can have varying degrees of scorch risk and those are the ones we consider here.

Firstly, fertiliser, being a salt, when in contact with the leaf of the grass absorbs moisture from it. This dries the leaf causing it to shrivel and therefore look like it’s been burned. The second is when either too much fertiliser is applied or moisture levels are too low. This causes a high strength fertiliser solution to develop in the soil and by osmosis ‘sucks’ moisture out of the grass plant causing a brown straw like burn.

High Grass Scorch Risk

This effect is increased when using combined grass ‘weed and feed’ fertilisers. By their nature they are a very fine granular or powder product to enable good contact of weed killer and weed leaf. This fine quality increases the contact area with the grass leaves therefore increasing scorch potential. Secondly if the lawn fertiliser is ‘quick release’ then it is all ‘active’ and has even more burn potential.

Minimal Grass Scorch Risk

On the other hand the salts in controlled or slow release fertilisers are ‘locked up’ to a certain degree thus limiting the dangers. Secondly, fertilisers such as Lawnsmith® Fertilisers are granules or pellets that will bounce or roll off the leaf into the soil thus minimising the amount of fertiliser contacting the grass leaf. This considerably reduces burn or scorch potential.

No Scorch Fertiliser

This is usually 100% coated and requires moisture to break down the coating and release the contents. These are normally used by lawn care companies because they need to safely feed lawns according to a schedule NOT according to the lawns requirements. This means they may need to feed your lawn during a hot dry spell otherwise they won't earn their fee. You, on the other hand, live close to your lawn and can feed it during the right conditions just like the greenkeeper or groundsman does to the turf he/she cares for.

Liquid Fertiliser

This refers to fertliser products in liquid or soluble form applied by sprayer or watering can.

Because these are already diluted by water they have considerably less scorch risk than dry powder products and next to no risk when applied when moisture is freely available in the soil and away from frost and direct sunlight. This applies to Lawnsmith Soluble Fertiliser and also Green-up Ferrous Sulphate at low to medium rates. However, it is normal and to be expected that Ferrous Sulphate applied at rates to affect moss always runs the risk of some slight temporary leaf burn. Any liquid fertiliser products applied when the lawn is short of moisture are also likely to scorch.

In summary

All fertiliser, other than 100% coated or 100% organic, has scorch potential with some doing it more readily than others. At Lawnsmith we have taken great care to balance our products so that the scorch risk is minimal as long as you apply when there is reasonable ground or soil moisture. If there is no moisture why waste your money fertilising - it won't do any good until the soil regains moisture!

What to do if you have Burnt the Lawn

You can’t remove the fertiliser as it’s already started to react and burn. The best thing to do is dilute it with water and stimulate growth so that the scorched leaves grow out. This means turning the sprinkler on and watering for several hours a day for several days depending on how much damage has been caused. The best time to water is straight after fertilising if you think you’ve over done it or when you first notice the damage and then continue with morning only watering.

Warning: If you use too little water you can dissolve more fertiliser which then doesn’t get diluted sufficiently which then burns new areas. When watering you must drench the lawn, area by area.


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