Hi and Welcome Angelee, Now you say that you have treated the back and front lawns both the same, BUT by any chance did you put more fertiliser on in some spots than others you know it is easy to do, especially on such a big area, because if you did and your lovely lush lawn has received too much nitogen it will make it weak causing it go yellow having a build up of too many salts in the soil.Test your PH

Also did you water the fertiliser in well, if you didn't that will burn the grass. You should never apply fertiliser on dry soil, water the lawn first, spread the fertliser then water in well. Hope this helps.
Cheers MM.

Thanks for the advice mistymorn. We haven't added any fertiliser to the lawns front or back. We laid a 50mm deep bed of lawn mix front and back (all the lawn mix was delivered and spread at the same time) before rolling on the turf and it has been watered since from our bore.

We do have a septic tank system and so there are leech drains in the backyard, could that cause excess nitrogen in the soil? There doesn't seem to be any pattern to the yellowing, some spots are up on the higher step of lawn, some on the lower, some very close to the house, some at the very back of our block.

If it is the leech drains causing the problem, any ideas how to combat that? can you buy a nitrogen neutraliser?

Thanks again
Ange

Hi again Ange. Well you know your septic system could be the reason for this, having one on our 1 1/4 acres in Townsville and I refused to have the tank close to the house so with plenty of room it was moved a fair distance away and I used to have this long line about 45cms wide that was always lush and green even in the very dry season.

And another thing Ange you mention bore water, you know that could have built up of a lots of salts in to too, sorry I dont know much about that kind of thing maybe you could find out, and do take a PH of the soil it should be around 6.5 - 7.5 for most things to grow.

I am surprised that you have not applied any fertlisers to your new lawn after having it down over four months, who knows maybe it may need some as the yellow could also be a sign of it lacking some trace elements then again it could go the other way like too much. I would ring where you got your lawn from and have a chat with them they should be able to put you in the right track reguards neutralising it if that is what is needed.

I hope it comes right for you and good luck.....MM.

Thanks mm, we will look into it.

Ange

You don't have a dog piddling on your back lawn do you Ange? That'll certainly yellow it.

Yep especially if its a Female.
After all the Males prefer the trees to the grass.
MM.

Nope, no dog, and the bore waters both front and back yards yet only the back is yellowing

Ange

lawn grubs?

What do they look like? I haven'r noticed any unusual bugs on the lawn... besides the occassional snail and slater but I will keep an eye out.

Ange

Apply a slow release fertiliser such as Scotts lawn builder,water in well and in a few days it will be lush and deep green.

Im surprised too that you havent used any fertiliser, and after 4 months it could definitely do with some. you might also have a few dry pockets that the water isnt penetrating, did you use a soil wetter at all? just check also that they arent high spots that the water is running off. if after fertilising it hasnt improved, then it might be best to dig out a small section with the spade and have a look underneath, check it see if it's dry and water repellant, check for grubs, but it may just be desperate for a good feed.

Check out this webisode about diagnosing common lawn problems: http://www.sirwalter.com.au/webisodes.html?task=videodirectlink&id=28

You could also have a look through the other webisodes on the Sir Walter website for information about fertilizing and and dealing with common pests and diseases & find information at the Love Your Lawn blog(http://www.sirwalter.com.au/info-centre.html).

Here is a link that might be useful: webisodes about Sir Walter lawn care