I have old pecan trees I'm trying to make productive again. Commercial orchardists in these parts routinely spray their pecan trees with zinc sulphate, to remedy a persistent shortage of zinc that plagues producing pecan trees. I don't want to do that, but I am wondering what plants I can plant that will help get zinc to my pecan tree.
I'm open to dynamic accumulators planted under the trees as well as green mulch crops grown nearby for chopping and transport to the trees.
I've done some searching and have seen several different plants listed as relatively high in zinc, including radishes, peas, napa cabbage, and amaranth leaves. But when I start Googling for numbers, I get radically different numbers from different sources, and it all seems to fall apart into unsourced rumor and received wisdom.
I'm hoping someone here will know. What are some crops that could be used to accumulate zinc for my pecan trees?
If your soil is low in zinc, then even plants that accumulate zinc may not be able to help. To help, they would have to be able to access some level of the soil horizon where the zinc is and bring it to the pecan roots. And since pecans have such deep taproots, it's unlikely that there is a soil horizon that they are not taking nutrients from. Which brings us back to importing zinc to take care of the deficiency.
But not to worry, there are easy ways to get zinc into the soil -- alkaline batteries. Yes, they are safe to compost, having no added materials that turn out to be toxic. Put out your own "Alkaline Battery Recycling" bucket, and let your friends and neighbors help you out. Since I developed this method, I never pass up the opportunity to pick up AA or C batteries that have been flattened in parking lots. One man's trash is another man's treasure.
If your soil is low in zinc, then even plants that accumulate zinc may not be able to help.
I agree with this. I hear so many people complain that their soil is lacking a nutrient, and want to find an accumulator to gather it. Dynamic accumulators cannot manufacture nutrients. They can only gather what they can find, which in a deficient soil may be zero. To gather any zinc, you would probably need an accumulator whose roots go deeper than your pecan's roots do. Most zinc accumulators are also trees - shagbark hickory, black cherry, red cedar, indicating that most zinc is probably no longer near the surface. About the only non-tree plant that that I know of that may help is the Coneflower Echinacea spp.
I get radically different numbers from different sources, ...
Once again, a radish grown in a zinc rich soil will have much higher numbers than one grown in a zinc poor soil. Nutrient densities in plants have a direct relationship to the nutrient density of the soil in which they were grown in.
Thanks for the feedbacks. I don't have a soil analysis, but my understanding is that the issue with pecans isn't so much a zinc deficiency in the soil as it is a very strong demand for zinc during nut production.
There are a lot of unknown variables here. Pecan trees do have deep tap roots for water, but the vast majority of their root system is quite shallow. Thus I do believe there's hope that a zinc-accumulating dynamic accumulator has the potential to be of assistance, by bringing up zinc from deep soils that aren't near the tree's tap root or any other part of its root system. Unfortunately I haven't identified a likely dynamic accumulator plant for this purpose yet.
I am interested to hear that red cedars are zinc accumulators. I'm not growing them under my pecan trees, but I have a lot of them growing elsewhere on the property and they often are crowding trees I like better. I wonder if it would be worth mulching them under my pecan trees?
Even if my pecan trees have consumed all the available zinc near them, I continue to hope I could grow zinc accumulators elsewhere and bring in the foilage as mulch. I just don't know how practical that is, or whether the necessary volumes are too large.
Thanks, John Elliot, for the tip about batteries. However it does seem to me not a big step from just breaking down and applying zinc sulphate from the feed store.
I've read on old-timey remedy was to hammer galvanized nails (zinc plated) into the roots of mature pecans. That might work for you. Another alternative is to fertilize with IRONITE, which is a ferilizer designed to correct metal deficiencies in alkaline soils.
But, as mentioned above by Jordon, it might be an issue of available zinc, which is pH dependent. You can get a simple pH testing kit at Home Depot for 5$ That will go a long way to help with the nutrition of your trees. I could do it by three different methods. I have ironite, can make soluble zinc spray, and also have nails.
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