Q.Lemon trees loss of leaves Cape Town south Africa
Last year, about March, I planted a lovely healthy Lemon tree. It seemed happy and established when it began to lose its leaves. It was getting plenty of water and I used organic fertilizer – Bounce back. I dug a nice square hole and planted using soil and compost. In spring (August – September) it flowered profusely but the early fruit soon fell off. It is flowering again, here and there. The few leaves remaining look healthy and green. No pests have been seen and the soil pH is 7.5 (tested with a soil measuring device). I have noticed of late that two of my dogs wee there. Could that be the cause of the problem? I know that lawns develop brown patches where the dogs have urinated.

Certified GKH Gardening Expert
It sounds like the problem is uneven watering. Citrus trees are deceptive in that they will not lose their leaves due to being to dry until after they have been watered after being too dry. Early loss of fruit is also a sign of the tree not having enough water for a period of time while in fruit. I would make sure that the tree is getting enough water, all the time. Also, remember to increase water to the tree while it is in fruit, as its water needs increase. This article may help as well:
https://www.gardeningknowhow.com/edible/fruits/citrus/leaves-falling-off-citrus-tree.htm