Burnett: Importance of proper drainage

Due to the hot dry spell we enjoyed this summer, it seems the issues normally associated with growing a nice lawn have been exacerbated.

I have been inundated this summer and fall with questions regarding turf problems both from home owners and maintenance people.

Due to the hot dry spell we experienced and enjoyed this summer, it seems the issues normally associated with growing a nice lawn have been exacerbated.

There are a few key things I look for when diagnosing turf problems and it depends on the symptoms displayed as to where I look first.

About 90 per cent of the time I am asked why the lawn is browning out or dying in patches or large areas. The other 10 per cent are questions regarding weeds, mushrooms, moss and variations of colour and texture.

Today I want to talk about the installation and the importance of proper drainage.

The B.C. Landscape Nursery Association has defined guidelines for soil composition and depths and if anyone wants a copy, email me at don@thegardenexpert.com. But here is a short version.

A properly installed lawn is one that has at least 10 cm of a sandy loam with about five per cent organic content. It is important the compacted subsoil is scarified and not left in a smooth condition after the initial excavation which causes a “perched water table.

It doesn’t matter how decent the top soil is, if the sub-soil is compacted there is no drainage and it is lack of drainage which causes so many problems with turf such as thatch build up.

Contrary to most thinking thatch is not an accumulation of dead grass clippings, it is an accumulation of dead roots that have come to the surface for air and then died due to lack of moisture. To test for proper drainage a percolation test is conducted by digging a small hole 30 centimetres wide and 30 centimetres deep, fill it with water and let it drain out completely. “Charging” the soil like this will give a more accurate reading than performing this test in dry soil. The next day fill the hole again and fix a ruler in such a way as to be able to measure the level of the water and gauge it as it drains out.

The ideal rate would be five cm per hour but anything between 2.5 cm and 7.5 cm is acceptable. If the rate is less than this a lack of air in the soil will encourage thatch buildup and several disease issues.

If the rate is faster it is difficult to keep moisture in the top soil causing the turf to become easily parched.

Sometimes browning out is associated with a simple deficiency of water due to a malfunctioning sprinkler system.

Test for even distribution of water by placing saucers or pie plates in strategic areas and comparing the rate of fill over a 10 minute time period. You might be surprised at the results.

I will continue next week with more on lawn issues including insect, weed and cultural practices.

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