Leaf Deficiency on Langsat.

[LangsatFL]

My Langsat is getting this yellowing on some of its older leaves.  Could someone please help me identify what I should be using to correct whatever deficiency my tree has.  The Langsat is 15 years old and is getting very tall now.  I am located in West Palm Beach if that helps with finding out what my soil is lacking for this tree.  I have another Langsat that is smaller that also has this same yellowing on the leaves.

[LangsatFL]

Here is a photo of my other Langsat that also had some sort of deficiency. 

[kh0110]

Yellowing of leaves with green veins could be iron deficiency and/or high soil pH. If on top of this yellowing, the leaves are also smaller than normal then it could also be a zinc deficiency. I would check soil pH first.

[elouicious]

based on pics here-

https://www.permablitz.net/articles/identifying-plant-nutrient-deficiencies/

I'd guess Iron Potassium or Magnesium

Have you done a soil or leaf test?

[LangsatFL]

Yellowing of leaves with green veins could be iron deficiency and/or high soil pH. If on top of this yellowing, the leaves are also smaller than normal then it could also be a zinc deficiency. I would check soil pH first.

I did a soil analysis this year and my soil pH was 6.8.  I sent the soil samples to a lab that was listed by the university of Florida.  Funny enough, the highest elements in my test were Calcium and iron.  Do you know of any good fertilizer I can buy that contains iron and zinc that I can use on my Langsats?

[LangsatFL]

based on pics here-

https://www.permablitz.net/articles/identifying-plant-nutrient-deficiencies/

I'd guess Iron Potassium or Magnesium

Have you done a soil or leaf test?

Would applying epsom salt suffice?  Or would it be better to just use Kmag since it also has magnesium?  Yes, I have done a soil test but I have never had a leaf test done on my trees.  Do you have any labs you could recommend for getting one done?

[kh0110]

Not sure but a pH of 6.8 could be on the higher end for Langsat. I believe where it originates, the pH is around 6 on average.

[LangsatFL]

Not sure but a pH of 6.8 could be on the higher end for Langsat. I believe where it originates, the pH is around 6 on average.

It might be too high. How do you recommend I lower it?  I use pelletized sulfur pellets a few times a year.  I have also drenched the soil with wettable sulfur. Is there any other method you would recommend I use for acidifying the soil?  I also mulch the Langsats and irrigate them daily since they are ultra tropicals from places that get rain totals that far exceeds what we get in south Florida. 

[kh0110]

The only sure way I know is what you already put in place, sulfur pellets. Maybe add more of it and less watering which could wash away the sulfur (?).
Another thing I could think of would be to spray something like this "Fertilome (10630) Chelated Liquid Iron and Other Micronutrients", if lowering pH is too hard. I use this for drenching but spray should do as well.

[Mike T]

Looks like Mg maybe induced by excessive use of an antagonistic macro like Ca. Maybe other nutrients in deficiency or excess I have a few trees.  PH of 5.5 to about 7.5 should be ok but winter mins below 7c can cause distress

[LangsatFL]

The only sure way I know is what you already put in place, sulfur pellets. Maybe add more of it and less watering which could wash away the sulfur (?).
Another thing I could think of would be to spray something like this "Fertilome (10630) Chelated Liquid Iron and Other Micronutrients", if lowering pH is too hard. I use this for drenching but spray should do as well.

Thank you for your advice.  I will look into buying some fertilome with micros.  I am afraid of foliage feeding Langsats since I burnt the leaves really bad on them one time even though I sprayed at night time and it was cloudy the next day.  I’ll probably just use it as a soil drench.

[LangsatFL]

Looks like Mg maybe induced by excessive use of an antagonistic macro like Ca. Maybe other nutrients in deficiency or excess I have a few trees.  PH of 5.5 to about 7.5 should be ok but winter mins below 7c can cause distress

Thank you for your reply.  Yeah, I suspected Mg so I have been drenching the trees with some epsom salt and also used some pelletized magnesium sulphate.  So far, the new growth still looks deficient.  My soil pH is 6.8 according to a soil analysis I got done.  Maybe you are on to something though.  My well water has a very high pH of 7.4.  Yeah, I know that this species hates the cold.  All my Langsats lose just about every leaf once the cold gets to 40F, especially if it is windy.