Wet roots, no doubt. You're on clay soil, and this to me looks like the typical response citrus will have to cooling temps and much too wet roots. I would suggest you plant your citrus trees on elevated mounds, to improve drainage. Remove all the grass from under the tree, and out to just past the drip line (edge of the canopy), as that's where your feeder roots reside. I would not just randomly water twice a week without checking to see if your tree actually needs that much water. Check the soil 12 to 18" down with a stake, and see how wet the soil is before watering, again.

Also, the grass is competing for available N in the soil, and it will always beat out the citrus tree roots, thus causing chlorosis. If the yellowing continues, see about treating for Phytothphora in the soil, which can proliferate if the soil is cool and too wet. Agrifos is a safe and effective soil soak treatment.

Lastly, you should be fertilizing with a good quality citrus fertilizer 4 times a year, and since you're moving into fall, I would apply just a light application, so you don't promote a late flush that could be damaged by frosty temps.

Patty S.

And check the pH of your soil; if it is over 7.5, you probably have to add chelated iron, as citrus cannot absorb iron from the soil at high pH.

There are reasons they don't grow citrus or wine grapes in Melbourne.

Hey Kans,

Sorry to hear about your citrus. You do have several things going against you here, water-retaining clay soil, transplant shock, and probably the most important factor is the cooling weather (autumn to winter in the southern hemisphere). As a last resort, you might try to dig up the tree to overwinter indoors in a pot. If you do that, don't mess with the roots too much, and water sparingly perhaps only once a week. the leaves will turn dull, but as long as they don't dry out, and you keep the tree alive, it will bounce back (will take a couple of months) and you could always replant in spring.

Hi All

Thank you very much for your suggestions. My lawn mower who is also a gardener told me its under watering issue but I am not convinced with that. He told how the roots are showing out and how the soil is cracked around trunk without enough water. I will continue with twice a week watering and apply nitrogen foliage spray.

Hi Kans,
As I told you in the other thread, the only thing that this doesn't look like being is underwatering. Clay will crack on the surface if it gets wet and then dries superficially. This is normal. You have to check a bit deeper. It is bad for citrus to water them if the soil is not almost dry espcially when grown in water retentive soils like clay. Dig a small hole inside that watering hole as far away from the trunk when you think it is time to water and check the humidity 10-30 cm below the surface. Roots showing superficially is not a big thing, citrus has very shallow roots. Citrus when water stressed curl their leaves upwards and if the stress continous they just drop them in a big way. Yellowing is not a sign of water stress. So regulate your watering initially not according to any fixed recipe but according to what you see in the soil. The plant appears also nitrogen stressed which may or may not have to do with too much water in the root area. See how it reacts to the foliar spray.

Remove the grass around the drip line and do not cultivate. If you have a very rainy season then that watering hole which appears too deep to me will become a water trap. The watering hole should be shallow and as large as the drip line. Ideally it should not be a hole but a wide ring so the area near the trunk stays relatively dry. Having a dry season when you need a watering hole and a very rainy season when that's a bad thing, is a big problem in water retentive soils. Rather than digging in the turf to create a depression, I would have created a watering hole by planting the tree shallower and creating a retaining soil mound. That could go away during the rainy season and reconstructed come the dry period. The way you have planted is problematic since not only you have created a water trap but you wll need to expand that deep watering hole to the drip line as the plant grows both for watering and for the plant roots not to be too deep.
Nik

Hi Nik
thanks for the suggestions. I will work on watering and I am going to fix the whole around the tree tomorrow. Hope it recovers soon.

I second the motion of removing the grass. Grass can put off a gas that is detrimental to citrus.

Tim, I have never heard of that. Grass uses nitrogen at a very demanding rate, thus robbing the soil of any available nitrogen for the less competitive citrus feeder roots, thus causing citrust to become chlorotic. Can you provide any data on that? News to me.

Patty S.