I have a couple questions regarding fertilizer that’s specific to my soils and am looking for some advice.
My soil is low OM sandy with a low N level. What would be the best option for a nitrogen source? I don’t want to apply dry fert and just have a it leach away. Would a CRF be a good option? A few of my trees (apple, pear) are going into their 3rd growing season. The first year I didn’t fertilize much or at all. Last year I top dressed 10-10-10 in the spring followed by a few applications of urea timed before a rain. Would this be a better option? I had pretty good growth last year with the additional N. I don’t think I have to worry about accumulating too much, but am concerned about over application. I can occasionally get manure, but don’t have a reliable source.
Second question is regarding mulch. I’ve been mulching with wood chips around the trees to conserve moisture. I’ve been doing a doughnut shape so there’s nothing touch the trunk. Is it okay to fertilize on top of the mulch, or is it best to rake it away first?
It is, but better if underneath. Some of the mulch will steal some nitrogen. No big deal.
Your regiment is fine. I myself every spring put fertilizer for my trees, cover with leaves, if I have them. I cover the leaves with compost. And if I have mulch I put it down.
I use a CRF I bought from AM Leonard. A couple times a year they have free shipping and I order a 50 pound bag. They have many CRF fertilizers in bulk. I’m still trying them out. So far the products have been impressive. I need something I can use on most of my plants, and this is working well for me. I have tried organics, and like them, I just cannot afford them anymore. I still use some for certain plants.
I wouldn’t place urea on top of wood mulch. It is apparently as much about volitilizatoin as bacterial consumption. However, this may be prevented if you do a thorough job of watering urea in after the application- I’m not sure.
For trees I’m establishing, I like to use the greenish coated urea with an approximate 90 day release period, but not on top of mulch if I can help it. If roots extend outside the mulch, you can always spread the fertilizer there. I don’t think it is necessary for the entire root zone to have access- trees adapt and roots reach for N in my experience.
For bearing trees I want rapid release and just for early spring. This helps fruit stick and size up without encouraging too much vegetative growth.
In the humid regions over time annual mulch can lead to too much available water and the release of organic N when you least want to be juicing up established trees- in the warm months.
Incidentally, wood mulch has ample K and I’ve never seen a tree suffer from a P deficit. Too much P, according to the lit, can create nutritional imbalances that are very difficult to correct. Never seen that happen though.- but then, I never supplement soil with it- against common recs- no matter what the soil tests may say. Call me eccentric, but I think P deficiency is almost impossible to experience because of mychorizal relationships.
The whole concept is based on experiments with sterile soils, IMO.
@alan - Thanks for the comments and good point on the P & K levels. My P levels are generally okay, but K are a little low. Good to know about mulch having high K. Is there a high demand for S or Zn in fruit trees do you know? Currently my OM in the soil is about 0.6%…
I’ve never had to deal with growing trees in a sandbox- that is extremely low organic matter. I suspect you could experience a wide range of nutrient problems of anything not abundant in the mulch. In my region the most often deficient micro is boron, but every region is different. Not a bad idea to do a test with the help of your county cooperative extension because they will be able to recommend an honest lab if they don’t do the test themselves through your states land grant U…
I have sandy soil.
The trick is to add organic matter without breaking your back or the bank. I save coffee grounds, save and dry banana peels, use alfalfa horse pellets, goat manure, and whatever else I can find.
I Keep throwing this stuff on the Wood chips. It would work a lot better if we got rain, but it’s still making a huge difference.
I spend very little on bagged fertilizer anymore.
It’s also important to realize that usually organic matter gives a lot more bang for the buck when applied as mulch than incorporated into the soil if labor or compost is limited. It disappears much quicker when incorporated.
I deal with a similar issue as yours here in coastal Florida. My soil is essentially sand. I have heavily amended my main beds with Organic matter just to make growing most plants feasible. My tropical stuff like bananas and papayas essentially grow in a compost pile. Citrus I try to keep on the dryer and less amended side. The trees I do fertilize I also like to rake it into the soil with some compost without disturbing the roots then add my mulch back on top.
We have rich soil here. You do not need to add anything. Normal top soil is much poorer than our native clay loam. It looks just like compost. I’ll trade you some soil for a few degrees of warmth?
Would you say most trees get nutrients from the feeder roots toward the surface? I’m planting some rows of berries next year too. I was going to get some compost and incorporate it, but maybe it would be just as good to use it as a mulch?
Not with trees, but most shrubs like it. So for the berries that would be fine.
Tree roots can stay and circle the good soil. Like for me our soil is so rich, top soil is not as nice. I use that. Use worse soil not better if fill is needed. I would mound the trees up too. I go 2 feet, it settles to about 1 foot above soil line…This year I’m using one of those fire pit metal rings as a raised bed. Last year it rained so much I had a problem with wet feet on my trees not in raised beds or mounds. Those trees were fine. Of the three at ground level one died, one was badly damaged losing a scaffold, and the third was fine but didn’t fruit. The ring is going where the one died. It’s about 2 feet above the ground now. Also best not to bury the tree deep. Root flares are desired.
When I was really studying this stuff I bought two separate soil text books based on agricultural use and read both a couple of times- a few things did stick. When a client has nearly pure sand soil I incorporate a lot in the soil AND use a top layer of pure compost under a thick 3-4" layer of wood chips or ground wood mulch, after planting trees just a bit shallow.
However if the budget only allowed either incorporation or spreading on top, I’d probably leave it on top, because overall that will give you more benefit if only because it lasts longer, but also because it leaves a pure layer feeder roots can grow into- rich not just in nutrients but also available water. Compost may also hold on to nutrients better if it isn’t mixed with sand.
Trees get nutrients from wherever roots are growing and they grow best where it’s warm and has a good balance of water and oxygen. These factors are generally most optimum in the top 18" of soil, but I’d say even more optimum in mulched soil in the top 6". It is easy to see where the growth of fine roots is most active, and it always looks most active right up to the surface with mulched trees in my region. In areas that get really hot they may not flourish so well right near the surface, but I don’t have experience at that.
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I have 5G buckets with dried banana peels, coffee grounds, rabbit poop, and egg shells. I’m thinking I should throw in some spent/moldy mushroom blocks, get some cool bags, and sell it.
OK, I get the picture. If I make it big with an amazing yield, maybe even bring some plants back from the dark side, you’ll say you knew me before I was famous.
