Looks to me like a nitrogen deficiency. But could be nitrogen+iron+ other micronutrients being deficienct. It's not always just one nutrient missing that is the culprit. What was planted previously on that land? Are there any large trees close by adjoining? The reason i ask that is because i have an area of land that has similar symptoms. The cause is a row of hau (sea hibiscus) close by with long extensive roots that rob all the nutrients from planted trees, no matter how many nutrients i poor in. Other trees with extensive root systems: albizia, and eucalyptus, for example can cause similar effects.
The land had tall grasses on it for approximately 7 years before I planted trees. Also a few small wild trees I cut out. Before that, it had sugar cane (no idea how it did in that location). The grass in the area looks normal. There are no large trees in that area, and the closest ones are the same species as other places on the farm.
I've been using half-rotted cow manure to help improve it, thinking the manure probably contains a lot of micronutrients as well as nitrogen. The grass has greened up from the manure, but I haven't yet noticed any improvement in the fruit trees. I don't have access to any micronutrient cocktail fertilizers but I can probably get something specifically targeting the problem if it can be diagnosed. My one neighbor never had this problem and had no idea what might be causing it.
My soil sample results will probably come back to me in a few weeks and I will share that here. When I had my overall farm
tested two years ago, the report came back with deficiencies as follows:
Phosphorus - low (1/5th recommended level)
Potassium - low (2/3rd recommended level)
Sodium - Low (1/4 recommended level)
Copper -low (1/2 recommended level)
Zinc - low (2/3 recommended level)
All else relatively normal. pH 6.5, Elect. conduct. low, carbon, nitrogen, calcium, magnesium, manganese and iron were in the recommended range. But, again, that the overall farm that is showing no signs of this problem. Maybe is the phosphorus and/or potassium as cbss_daviefl suggests. This area may just be more extreme. The other possibility is that the bedrock is somehow poisoning the soil in that area.