I live on the east coast of Australia and its now early winter. I planted a lemon tree (thought it was a myer but it has thorns) from the nursery about 12 months ago and now SOME newer leaves of my myer lemon are becoming
twisted and yellowing. I have been removing them but it hasn't stopped.

Not all leaves are doing this and otherwise the tree looks quite healthy. I put some robust compost around its base and heaped it up. It is now beginning to show signs of bearing fruit.

It is in the back yard with plenty of sun located about 400mm of earthy soil which I cut in through a clayie base crust to reach the sub soil underneath then surrounded this circular hole, which is about 1 metre across, with villaboard which I bent into a circle to stop the grass growing into it. It acts like a border and is easy to whipper snip around.

It had a nitrogen deficiency which I fixed but now am worried about this yellowing factor. I really want this tree to succeed. I have taken a photo of these leaves but not sure if I can load it with this info. Any suggestions?

Is it the older growth thats yellowing or the newer?

I noticed that the leaves are somewhat distorted. This could be part of the problem.
Leaf miners, citrus thrips, and aphids will cause distortion by sucking the "juices" out of the leaves. The leaf miner larve burrows inside the leaf as it feeds. Have you noticed any "bugs" on the tree? Look with a magnifying glass to inspect every leaf and stem. Mealybug will also cause distortion and may cause death to the tree if not controled. Mealybugs will leave cottony looking substances on the leaves and stems.


"It had a nitrogen deficiency which I fixed but now am worried about this yellowing factor"

Yellowing is not always caused by a nitrogen deficiency. There may be planty of nitrogen in the soil but the plant is unable to utilize it due to a lack of magnesium or other mineral. Sometimes the Ph of soil is too high or too low that it literally "locks" the nutrients and makes them unavailable to the plant.
Andi

NEVER EVER EVER heap anything up around a citrus tree. keep anything and everything away from the trees trunk. you could cause it to start rotting!!! I would remove it right away. that could be part of your problem.

The base of the tree trunk should not be covered with anything,soil,compost,mulch. This will as CC said lead to foot rot or girdling. You can incorporate the compost into the soil,being careful not to overly disturb the shallow growing roots. You could also make a compost tea and water the tree with it. This will cause a lot of the nutrients to leach out of the compost into the water.