Hello Kans. when you say planted, do you mean inthe ground or repotted to a new pot?

I bought them from nursery and planted them in ground.

Could you post a pic? Could you tell us what your soil is over there? Could you tell us what your weather is like currently, if there have been abrupt changes in weather and whether the plant was taken out of a greenhouse or transported from an area with different microclimate? Could you tell us if the soil dries out or not between waterings? How long have you had the tree planted? Is citrus commonly grown in the ground in your area? Have you planted the tree deeper than it was in its pot?

Citrus are notorious for getting a shock due to abrupt changes in environmental conditions. In general they recover if conditions eventually suit them.

Finally, it would be a good idea if you posted ths in the citrus forum.
Nik

This post was edited by nikthegreek on Wed, Mar 19, 14 at 0:51

Here is the link to a previous Citrus discussion on Gardenweb Australia

Here is a link that might be useful: Citrus in Australia discussion

We have clay soil. It been a month since we transplanted from the pot. I think it was a bit of shady position in nursery. Now its in full sunny position. Its autumn now. We had a couple of dry days but I never failed to water twice a week as suggested by local nursery. We live in Melbourne , Australia. Citrus are very common here. Hope this helps.

Few more pictures

Few more

Did you look at the Link? Your plant is suffering from some sort of deficit. Have you got some complete Citrus food because now is the appropriate time to apply.
Here is a pic of my lime tree behind the orchid. Note the deep green colour of the foliage, a bit deeper green than on a lemon or orange tree but those yellow tones on on your plant indicate some sort of nutrient deficit.
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First thing, the plant is not dying. One thing I can say from the way it looks, the plant does not seem to be suffering from drought. The opposite might be true. Unless the soil gets almost dry in a depth of about 10cm near the base of the trunk I would refrain from watering. If that were an established tree I would be tempted to say it needs some nitrogen fertilizer, but this is clearly not an established plant so I would refrain from providing any fertilization through the roots until I saw sure signs of new growth. I would try to control my watering in case the plant gets waterlogged, spray with a weak nitrogen foliar feed a couple of times and just wait. Shocked citrus may loose all their leaves and then recover with new growth.
Nik

This post was edited by nikthegreek on Wed, Mar 19, 14 at 6:28

Yes, this is exactly what happened to my lemon........it actually defoliated more or less completely, only putting out decent new leaves in its second season. It is taking me ages to get the balance just right - watering, I think, was a major issue - and I am still struggling with the nutrient balance (mine is in a pot).
Kans, I would also be inclined to remove the ring of turf from the base of the tree - they resent competition and need a free area at least as wide as the drip line (especially in a small establishing tree)....and after a good soak, would be tempted to apply a decent mulch (anything will do, even those grass clippings at a pinch. I think a foliar spray of a specific citrus fertiliser, applied in the evening, might be a very good idea.

Don't panic (yet) - mine looked diabolical for its first 2 seasons and is only now picking up - I suspect these trees resent transplanting or any changes to their environment.

Thanks for the suggestions and will work on watering schedule.