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I had a question and couldn't find the answer on here.

I have apple trees I've been struggling with for a few years now, between deer, caterpillars, and other things. I've got recommended fertilizer rates and times of the year, depending on their age, from the growers I purchased the trees from.

The question I have is about fertilizing them I have mulch down. I've had some people recommend pulling mulch back, fertilizing evenly, and putting the mulch back in place. I've heard others say you can put it in a ring around the outside of the mulch and it'll seep in to the roots. I've also heard that you can scatter it right on top of the mulch and it'll be fine.

I want to know which of these is correct or if all of them are. My inclination is to say that I just add the fertilizer to the top of the mulch and water it right after. I feel like it'll travel right through the mulch to the roots, just like rain water does. I think pulling the mulch back would potentially disturb roots and I think that putting a ring of fertilizer around the perimeter of the mulch might burn something. Let me know what you guys think. Thanks.

Also, this is just a regular balance granular fertilizer. I don't think it's slow release. The mulch is wood chips, 3-4 inches deep and 6 inches around the tree base. The recommend fertilizing (3) times a year at the end of March, beginning of June, and the end of August here in SC. I think it's something like a half pound for every year old it is, not to exceed a certain number of pounds. I'm pulling that number out of my hat, though. I have it written down somewhere, I just wanted to give you an example of how I'm doing it.

  • what is the formulation of the fertilizer, that is, is it granular, capsules or liquid? What's the mulch material and how deep is it? – Bamboo Jan 31 '17 at 15:13
  • Granular fertilizer, wood chip mulch, 3-4 inches in a 6' diameter. – Dalton Jan 31 '17 at 15:29
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As you've noted there are differing opinions on this subject from reputable sources which likely means that all methods work, though one would think that direct mixing into the soil would be the most effective. Some people also advocate making drills into the soil and placing the fertiliser at equidistances along the drip line. If you have an orchard of trees, then it's likely you're not going to bother pulling back any mulch as it may be too time-consuming. Some fertilisers say that if you're going to apply it over a thick layer of mulch, then you need to double the amount applied.

Wood based mulches placed on the surface of the soil don't take up significant amounts of soil nitrogen. Their decomposition is primarily by fungi whereas nitrogen drives bacterial decomposition. But if you mix that mulch into the soil it will tie up some nitrogen presumably as the decomposition elements change until the process is complete when it's released back into the soil.

It's thought that soil fungi can form a bridge with their hyphae to reach the surface mulch and transfer small amounts of surface nitrogen to those parts of themselves feeding on the mulch.

  • I don't have an orchard. I've got about 4 trees of varying types, so I could pull back the mulch. I just didn't want to do the extra work, because they're fenced. I would be worried about damaging the roots trying to mix it into the soil or drill holes for it. The closest I ever came to that was using those fertilizer spikes you hammer into the ground. – Dalton Jan 31 '17 at 21:38
  • @Dalton apart from being told that they need to be fertilised, are the trees actually showing any signs of deficiency? And if you scrape away some of the mulch, does it look as though it's decomposing and feeding the tree roots for you? – Graham Chiu Jan 31 '17 at 23:01
  • The mulch is breaking down, but not very fast. I've been having a hard time with these trees and couldn't tell you whether or not they're deficient. I could barely tell what the leaves looked like for a couple of years, because inch worms were decimating them. I started getting that handled, but they're still very small. I've finally started to see some decent growth, but they were given to me by a family member and came only a couple of feet tall. So no, I'm only basing my fert. schedule on the nursery recommendation. I will probably send a soil sample to my local ag extension this year. – Dalton Feb 1 '17 at 13:25
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You've said its wood chip mulch - if that's fresh wood chips, it will be stealing nitrogen as it decomposes. The fertilizer, if its granular, probably takes around six weeks to break down, releasing nutrients gradually as it does so. Were they my trees, I'm afraid I'd rake off the mulch, gently - if you find root material penetrating the mulch, then you'll have to stop, but assuming you don't, rake it off, apply the fertilizer, then immediately reapply the mulch over the top. No need to turn or dig the fertilizer in if you put the mulch back. Alternatively, I'd choose a liquid feed, applied over the mulch, more often.

You could choose to simply rake off the outer ring of mulch, apply the feed there, and then replace that, but I'd still choose the most difficult method, sorry! Others will probably have different ideas...

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