I agree with BP and Dori. It's unusual for there to be an Fe deficiency because soil Fe is inadequate. Fe is generally deficient because high pH causes Fe to form insoluble compounds with other elements, or because other elements are found at very high levels in the soil and are creating an antagonistic deficiency (P or Mn are the prime antagonistic offenders). You can take steps to lower soil pH by adding organic matter or by using other pH lowering elements/compounds (FeSO4 is one, but be careful - it can cause an antagonistic Mn deficiency), or you can apply some form of chelated Fe with Mn, which is less affected by soil pH. What makes you think you're dealing with an Fe deficiency? Al

Gwarb: I'm enjoying the discussion on this topic, seems for a portion of GW dedicated to soils there isn't a great deal of focus on them. I finally had the thought of going to one of the country's land grant sites who commonly deal with both fruit tree production and calcareous soils, as it happens I used to live there and opted to go with the more familiar. CSU had some interesting info. including: 1) AB DTPA results and suggested Sequestrene 138-Fe app rates in lb/sq. ft. 2) the suggestion to not bother applying Zn to the soil but instead do a foliar spray with Zn sulfate just prior to bud break, interesting indeed. For grins I looked up MSU and U of VT's leaf tissue data and found not as much difference as I expected, maybe they borrow each other's table values, beats me. I snickered when you wrote about tearing up the trees and starting over AFTER starting off on the right foot dealing with the soil. When people around here ask me about planting a fruit tree I jokingly tell them to start when you are young. Between the mistakes made with the soil, pruning, pest control and cultivar selections you may be starting all over more than once. Maybe in my next life I'll major in Pomology at school and start the orcharding MUCH EARLIER. Methinks the amm. sulfate will be a very good choice for an N source as it will also help to some extent with the pH issue. On that topic, one question, I know the amm. sulfate will donate H+ ions to drop the pH but am not absolutely positive about the fate of the sulfate in that respect. It seems to me that the S will be freed to form H2SO4 which would obviously aid in dropping the pH but to do so it would have to get the H+ from somewhere, from a soil chemistry standpoint the net result would be zero as far as the balance of H+ (and pH) in the soil. What does become of those darned sulfate molecules, I just don't remember? Just remembered, good idea in, I think the other post on this topic, the notion of putting holes in the ground around the drip lines and filling them with a Fe fert. like Fe sulfate. It just so happens I have a JMC Backsaver soil probe that would work very nicely for the task. Now for the hard part, what to mix the fert in (if anything) and how much goes in the hole? I would fill the holes from top to bottom (probably somewhere between a 12-18" deep holes). Good answer to 41 north's question. Hey 41north: never heard of vertical mulching, what is it? I've been heaping about 6-12" of wood chips down the tree rows per year for the last 3 years now, that stuff has been biodegrading to about 1" deep over the summers. I expect with enough years that beautiful dark layer will slowly become deeper and deeper. The worms sure have been busy under the mulch layer taking it down their holes, some holes are big winoug to stick my finger down. One of these summers when I expose one of those big holes I intend to take my 4' long prod rod and gently slide it down the hole to see hoe far it goes down.

Looks like micro nutrient deficiency. This is commonly caused by alkaline (hi-calcium) soil, subsoil or water. If this is the case, the best solution is to start checking for the cause before feeding more minerals (which will only become unavailable). The water is easy to check with a pool test kit. Sometimes it is buried building materials (concrete). Look for small pieces of natural limestone. Or it may be alkaline clay (look for yellow clay in the subsoil). While you're doing this, spray with a solution of 2 tsp. each of the following; Epsom salts (magnesium sulfate), Zinc sulfate, and manganese sulfate in 1 gal. reverse osmosis water. The magnesium may not be unavailable but just swamped out by an excess of calcium. A polymeric spreader sticker can be helpful. Especially if a tsp of ferrous sulfate is added. You will probably not find manganese readily available except where palm trees are sold in large numbers. Some micro nutrient sprays for citrus are available. Southern Ag makes one sold in the gulf coast region. EDTA chelated chemicals are not effective. Long term solution is addition of soil sulfur. This is hard to do without soil samples. It is easy to go too far and have a worse problem.

Thats good that you can manage pH soon. I measure three things: pH, EC, and temperature. Once I decide on my fertilizer solution concentrations and can make the solution, I don't give the EC very much attention unless there has been a rain, and by using the EC I can confirm how much rain fell into the solution, but this is just fun to do and not essential for me. At the moment where I live it is cool weather and I do not have much evaporation of water from the solution. Today was the warmest day, at a high of 19C! Warm! On the other hand in someplace like Mysore,19C will be the humid night low temperature, but you may be a very dry 32C in the afternoon when your relative humidity can easily fall to 32% - which is a warm desert situation. At that time there will be a lot of general evaporation and transpiration of water into the air from the plants. So you will need to be sure your total solution stays a same volume of water, or the nutrients will concentrate a lot if too much water is lost into the air. That is nothing I am worried about, but your weather probably presents that situation. An EC meter can be very helpful to know for sure what is happening, but if it is difficult or expensive to get one, you can do without it as long as you start with the right fertilizer strength (and not too hard water, or not too salty if close to the coast), which will depend on your source preparation of water, and you regularly add water (or allow rain to fall in like I do) to the solution as it is lost by evaporation to maintain the same volume. Finally, to do without an EC meter another tip is to have at least 2.5 liters per plant for light feeders and 5-6 liters per plant for heavy feeders. This will insure a larger reservoir of fertilizer is always available and it will attenuate fluctuation of EC during the cycle. You can keep it longer before changing too, which is more convenient ;)