front lawn

(Question)

Hi Masters, put in new sod on new soil on our front lawn two summers ago. Old lawn was developing too much thatch. Perhaps over fertilized it since it started to yellow within a few weeks. Ever since it has got progressively worse. Test showed super high alkalinity. Did I cause this by overfertilizing? It has been almost two years. What next?

(Answer)

Several factors may be to blame for your yellow lawn.  Trying to determine the true cause, in order to treat the problem correctly, is crucial. A pH imbalance can result in nutrient loss. Lawns suffering from nutrient deficiencies commonly have yellow leaves.  You indicated that you had a soil test and it showed super high alkalinity.  Iron chlorosis is a common problem in overly alkaline soils (pH above 7.5). This means that iron is unavailable to plants. In your lawn’s case  – the blades of grass. To lower the pH level, you can apply aluminum sulfate to the soil.  Depending on the size of your lawn you may wish to seek the services of a professional lawn care company to carry out this task. There are lots of them around.  (Unfortunately,  Master Gardeners cannot recommend specific companies for paid work since we are volunteers with a mandate to educate the public about gardening and horticultural issues). If the lawn is still yellow after treatment, then there’s another factor at work. Drought or dormancy can lead to a yellow lawn.  Your lawn needed to be watered thoroughly during the early growing period to ensure deep roots. If this wasn’t the case it can cause yellowing of the leaf blades. It could also be an infestation of grubs. To determine if this is the case grab hold of a clump of grass. If it pulls away easily it could be that.

For your information the following documents produced by the Ontario Ministry of Agriculture, Food and Rural Affairs provide a wealth of information on lawn maintenance  see:   https://www.omafra.gov.on.ca/english/crops/facts/08-017.htm and https://www.omafra.gov.on.ca/english/crops/facts/08-021w.htm