Why is this tree yellow?

[edweather]

We have 5 citrus trees, all fairly young.  Four look good, but this one is apparently stressed a bit. It's a bit of a frankentree. We started a seed from a Cutie, and grafted honeybell, and red navel to it. The other four trees were purchased from a nursery.  It's about 4 years old, but this is the first time it has looked like this. There are other trees in the neighborhood that are a bit yellow too. Was hoping it would just clear up on it's own, but has been like this for months. Any help is appreciated.

[Millet]

has the tree been fertilized?  The leaf pattern  is show a nitrogen deficiency. A 4-year old citrus tree should be fertilized 3 times a year   

[edweather]

Yes it has been fertilized. Three times per year, like the others. The other trees are a nice dark green. The soil is sandy, and tends to be a bit alkaline. I added a little sulfer and iron to the soil today. It's basically been yellow all year. Should I try a little more fertilizer?

[Galatians522]

This is probably not a good time to fertilize with nitrogen in your location because it will make your tree flush. Flushing trees are much more susceptible to cold. Citrus leaves live for about 2 years, so you may see some yellow leaves for a while even after you are able to fertilize in the spring. Watch the new growth--that should give you a read on the tree's current condition. Also, as you may be wondering, I imagine that the difficiency is more noticable on that tree because of its rootstock. The other purchased trees are likely grafted to more vigorous (and probably better adapted to your alkaline soil) rootstocks that are better able to scaveng and uptake nutrients. That's my 2 cents.

[edweather]

Thanks. Yeah, the rootstock is definitely questionable. Kinda upsetting, because it has grown well to this point and has some oranges this year. Hopefully it will clear up. FWIW, the backside of the tree looks better. The side that gets the sun is worst. If it does die, we can replace it with a good tree.👍👍

[Galatians522]

By the way, some of the groves around here spray vinegar on the soil to help with ph.

[Millet]

Vinegar is an organic acid (acetic acid) generally with an acid content of between only 5 to 8 percent.  Being an organic acid it has a very short life span.  The growers in my area use phosphoric acid. Many growers also use sulfur.

[Galatians522]

Vinegar is an organic acid (acetic acid) generally with an acid content of between only 5 to 8 percent.  Being an organic acid it has a very short life span.  The growers in my area use phosphoric acid. Man growers also use sulfur.

Indeed, sometimes the commercial groves add sulfuric acid to the irrigation water to adjust the ph, but that is probably outside the scope of a homeowner. Phosphoric acid sounds like a really good idea--you can adjust ph and fertilize at the same time!