Citrus are heavy feeders, requiring more nutrition than most trees. Not only are the tree's new leaves pure yellow, many of the older more mature leaves throughout the tree are also showing to be deficient., Grow your tree as you wish, but my suggestion is to feed the tree with conventional fertilizes. Looking at your pictures, it is easy to determine that the tree is suffering from a drastic deficiency of nitrogen, and probably a few other elements. You don't say how old the tree is. A 1 year old citrus tree should be fertilized 6 times /year; a 2 year old tree 5 times /year; a 3 year old tree 4 times and a 5 year old tree and older 3 times a year. I would suggest that you purchase a conventional fertilizer with a formula such as 8-8-8 and fertilize the tree, covering the entire area of the tree's root zone once ever two months during the growing season. Your tree is so badly undernourished you might even give it a urea foliar spray. Good luck to you and thls tree,