Applying Zinc To Pecan Trees           Fertilizing Pecan Trees          Watering Pecan Trees
If you do nothing else to care for your pecans trees, water them regularly and apply zinc applications throughout the early growing season.  It is my firm belief that there is nothing more important if you are to achieve a successful pecan crop year after year. 
There are two methods for applying zinc, one is what I believe the correct method, the other I believe is the wrong method.  The 'nut gurus' for the most part tell us we can either apply zinc sulfate to the soil beneath the tree or apply it to the leaves in liquid form.  I suggest you forget about dumping zinc on the ground, probably a useless and money wasting process, and spray your tree foilage with zinc, what I call 'Zinc-ing the trees.'
To zinc your pecan trees with my preferred method, you will, of course, need a sprayer of some sort.  If you have only a few trees, or if you have a whole orchard of young, small trees, you may opt for an inexpensive pump sprayer, although sooner or later, you will find it necesary to 'move up' to a more efficient and easier to use mechanical sprayer.  I personally attempt to run my pecan operation in 'the black' and therefore, have generally worked my way up to larger equipment only when the profits from my orchard permit me to 'pay cash' for equipment improvements.
Whatever sprayer you choose to spray your zinc with, keep in mind that you will either need a high volume of pressure to reach to top parts of your pecan trees, or will need 'some height' to elevate you and the sprayer to a level of your trees' branches.  If you choose a smaller sprayer, you may find that riding in the back of a pickup up and down your orchard rows will work nicely.  I rig my sprayer onto our old Farmall 560 and take off down the rows, spraying each tree with a zinc solution.
Ah yes, the zinc solution.  Zinc Sulfate can easily be found at most home and garden stores in quantities as small as one pound.  It is a powder that dissolves well in water, and a little actually goes a very long way in terms of applying it to your trees.  Liquid Zinc is also available, however it tends to crystalize over a period of time and I've found myself discarding jugs of zinc.  I personally recommend the powdered zinc because of this.

Symptoms of zinc deficiency
To spot zinc deficiencies, look for small leaves which curve or curl, leaf edges that are 'wavy,' discoloring in the 'veins' of the leaves, and most noticably from a distance, long bare branches with small 'clumps' of leaves at the top, or even dead branches with no leaves.  Signs of zinc deficiency in the nut are poorly filled kernals and ' hollow pecans.'  However, I assure you if you adopt a pecan orchard management program that includes regular zinc applications, you will not find these symptoms in your orchard.
When to apply zinc
Since we've decided to apply zinc directly to the leaves of your pecan tree, obviously the first application must wait until the spring leaves have appeared.  Apply your first application when your trees 'look like' they have leaves on them.  Pecan leaves appear first as light yellow-green foilage.  This is the optimal time to make the first application.  Avoid spraying your trees in the heat of the day since the zinc has a tendency to 'burn' the leaves.  Mix your zinc solution according to directions on the package and spray the entire tree until you see 'it raining' beneath your tree.  (Maybe just sprinkling.)  In other words, coat the leaves of the tree sufficiently for some of the zinc solution to drip from its leaves.
Additional zinc applications should be made every two to three weeks until the first of June.  These early season applications should be sufficient to supply your trees' zinc requirements.  If you determine your orchard requires pesticide treatment, most pesticides can be mixed into your zinc solution and applied concurrently.

Summary
Zinc applications must be at the top of your list of priorities when it comes to pecan orchard management.  Not near enough attention is given to the importance of zinc in the production of pecans.  Zinc is an inexpensive and easy to apply nutrient, and the benefits reaped are more than worth the expense and time it takes to supply your pecan trees with one of the best kept secrets to pecan production success.  Zinc your pecan trees!
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Signs of zinc deficiency in pecan trees
Symptoms of zinc deficiency in pecans
Bare, leafless limbs
or limbs with small
clumps of leaves signal a zinc problem.
Curling leaves
with 'wavy edges
are a sign of zinc
deficiencies
pecan tree sprayers