It is a lemon tree, though it is hard to tell what variety of lemon it is. If the fruit was very wrinkled and bumpy, it might be a rough lemon, which is often used as a rootstock, but its fruit is too dry to be used the same way as regular lemons. If the fruit was smooth, the problem might be the general poor condition of the tree. I would feed it regularly with cottonseed meal and/or fish meal, plus a little Epsom salts, and driving large galvanized nails into the ground at the drip line, about one every foot along the drip line. Watering is going to vary with your climate: In the desert or semi-arid scrub, you would want to water deeply about once every two weeks in summer, and once a month in winter. In coastal climates, or the more humid north, also water deeply, but half as often. Here in Phoenix, I would suspect a Phytopthora infection of the trunk and/or root crown, but I don't know if there is a similar disease there in Oz.

Thanks for your ideas. Really apprieciate the tips.

You're welcome, Clayfield!

Nice answer, Tug... I'd be suspicious of trouble at the root too...

Here in the U.S., it is usually a disease known as gummosis, but I have no idea if that, or a similar fungus, is found in Australia. Thinking about it, nematodes could cause similar symptoms, and would cause irregular bumps on the smallest roots, which makes them a little easier to diagnose than most fungi! One possibility to eliminate. Nematodes are a little more likely in very sandy soils--clay tends to suppress their pretensions.

It does have alot of bumps on it. Is it worth bothering with if it is a rough lemon? Im only learning about plants and it's in the best sunny growing spot in my yard. What can I do with it?

Well, if you can get it healthy again, so it actually bears fruit, the zest is still good, and you can make preserved lemons, in the Mediterranean style. Plenty of good lemon flavor, just very little juice to go with it. If it was me, I would replace it with a 'Meyer improved' or 'Eureka' lemon--'Lisbon' instead of 'Eureka' in desert areas.

I think i will remove and replace it. Thanks. I dont have endless space and I would rather enjoy the fruits of my labour. Hubby will be thrilled... Pull it out.

I would either plant the new one at least 2 meters away from the old stump, or remove all dead roots from a volume at least 1/2 m deep, and a meter across. Dead wood fermenting underground can poison the roots of the new tree for the first year or two.

It's also wise to keep an area of around a foot to 18 inches at the base of the tree clear of anything else growing, including grass, so it doesn't compete with the tree roots for nutrients... put a mulch on the bare soil instead, to keep moisture in, if that's an issue where you are.