The verdict’s in, yes you can.
But, and there’s always a but you should aim for the ground around your tree, and not the trunk and water it in well so it dilutes and doesn’t get smelly.
In fact, there is a whole study devoted to turning human urine into fertiliser, so if you are doing it now, you are ahead of the game.
One researcher described it as ‘liquid gold’.
While it’s good to pee on your lemon tree, don’t pee on your lawn. Your lawn isn’t able to cope with the concentration of nutrients, so save it for the trees.