Fertilizing oak trees.
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T-Max
5 year old buck +
There was a study done on this that I think Bronson Strickland referenced on a podcast. I will attempt to sum it up. They crown released some mature oaks, crown released and fertilized some, just fertilized some, and had control trees where they did nothing. The conclusion was that the best thing you could do was crown release them for more acorn production. Fertilizing them also had little additional benefit if any.
Edit: It was Craig Harper
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The Fishman
5 year old buck +
Here is the research paper that T-Max referenced. Below is the abstract.
Forest management practices that influence mast production in oaks (Quercus spp.) are ecologically and economically important for regeneration of future oak forests, timber products, and wildlife that consume acorns. We conducted a 10-year experiment in upland oak-hickory forests of eastern Tennessee to determine the influence of canopy release, fertilization (addition of nitrogen, phosphorus, and potassium), and their combined influence on white oak (Quercus alba) acorn production, acorn size and quality, and acorn depredation. We used a robust before-after-control-impact design where we collected pre-treatment acorn production (acorns/m2 of crown) data from 120 white oaks for 5 years, applied canopy release and fertilizer treatments and then monitored post-treatment acorn production on the same trees for an additional 5 years. Acorn production was temporally variable with 6 of 10 years being near complete mast failures (≤3.67 ± 8.52 acorns/m2 of crown).Also, production varied greatly among individual trees with 11% of trees classified as excellent producers accounting for 31% of all acorns produced, and 41% of trees classified as poor producers accounting for only 17%of all acorns produced. Canopy-released and canopy-released-and-fertilized trees increased acorn production65% and 47%, respectively, following treatment relative to control trees, with effects greatest in trees classified as poor producers. Fertilization did not influence acorn production or size and did not consistently influence acorn quality. Furthermore, acorn depredation rates did not differ among treatments. Our results indicate crown release is an important management practice when management objectives include increasing white oak acorn production in closed-canopy conditions, whereas fertilization does not influence acorn production.
Forest management practices that influence mast production in oaks (Quercus spp.) are ecologically and economically important for regeneration of future oak forests, timber products, and wildlife that consume acorns. We conducted a 10-year experiment in upland oak-hickory forests of eastern Tennessee to determine the influence of canopy release, fertilization (addition of nitrogen, phosphorus, and potassium), and their combined influence on white oak (Quercus alba) acorn production, acorn size and quality, and acorn depredation. We used a robust before-after-control-impact design where we collected pre-treatment acorn production (acorns/m2 of crown) data from 120 white oaks for 5 years, applied canopy release and fertilizer treatments and then monitored post-treatment acorn production on the same trees for an additional 5 years. Acorn production was temporally variable with 6 of 10 years being near complete mast failures (≤3.67 ± 8.52 acorns/m2 of crown).Also, production varied greatly among individual trees with 11% of trees classified as excellent producers accounting for 31% of all acorns produced, and 41% of trees classified as poor producers accounting for only 17%of all acorns produced. Canopy-released and canopy-released-and-fertilized trees increased acorn production65% and 47%, respectively, following treatment relative to control trees, with effects greatest in trees classified as poor producers. Fertilization did not influence acorn production or size and did not consistently influence acorn quality. Furthermore, acorn depredation rates did not differ among treatments. Our results indicate crown release is an important management practice when management objectives include increasing white oak acorn production in closed-canopy conditions, whereas fertilization does not influence acorn production.
TreeDaddy
5 year old buck +
lotta variables in that abstract to consider
Variable production with 6 of 10 years mast failure, variable production of individual trees, variability of soil in different forests
How were these accounted for in the statistical analysis of the results ?
I applaud the efforts of the authors, but doubtful that "fertilization does not influence acorn production" is an accurate statement
bill
Variable production with 6 of 10 years mast failure, variable production of individual trees, variability of soil in different forests
How were these accounted for in the statistical analysis of the results ?
I applaud the efforts of the authors, but doubtful that "fertilization does not influence acorn production" is an accurate statement
bill
Bowsnbucks
5 year old buck +
I can only attest to our camp fertilizing a big, old white oak tree at the end of a field. We scattered a 50 lb. bag of 10-10-10 around the tree after lightly discing around it. The couple years we did that, we had banner acorn production from that tree. Crown was already open and free, and spans about 40 to 45 feet.
bigboreblr
5 year old buck +
The last house was on 3 acres. I only had maybe 4 or 5 oak trees. What really made a different was providing water during bad dry spells.
IF you have a 275 tub and a pond / pump. IT would be worthwhile watering a few trees, especially if you using that spot for a close bow n arrow shot. When it got bad, each day I would run a hose for 15 minutes or so. A year or two later, I connected a hose to the gutters and put a few 55 gal drums n there. I would dump them over during a dry spell.
I did fertilize some too. Maybe 10-15lb on a 18" diameter tree or so.
I small game hunted quite a bit back then about a mile down the road in the state forest. Day and night differences on dry years. Definitely see the difference in deer and squirrel acivity at the house too.
IF you have a 275 tub and a pond / pump. IT would be worthwhile watering a few trees, especially if you using that spot for a close bow n arrow shot. When it got bad, each day I would run a hose for 15 minutes or so. A year or two later, I connected a hose to the gutters and put a few 55 gal drums n there. I would dump them over during a dry spell.
I did fertilize some too. Maybe 10-15lb on a 18" diameter tree or so.
I small game hunted quite a bit back then about a mile down the road in the state forest. Day and night differences on dry years. Definitely see the difference in deer and squirrel acivity at the house too.
The Fishman
5 year old buck +
There is a materials and methods section in the linked paper that discusses how they performed the experiment, how they selected three different sites in order to have replication of treatments, how they studied the trees for 5 years before the experiment, and how they classified the trees into different treatment groups based on previous acorn production. There is going to be variability in any scientific study. Experimental design will account for the variability and allow researchers to draw statistically valid conclusions. For this study on 120 trees at three different sites, the researchers found that "fertilization does not influence acorn production" was not only accurate, but statistically valid.
I would encourage everyone to read the entire study as there is lot of good information on variable acorn production amongst trees within the study. This characteristic has been studied in other oak species and really should make us all selective in the trees that we plant. You really want a seedling produced from a tree that is an excellent acorn producer and not just a random seedling.
omicron1792
5 year old buck +
Yeah I agree. @TreeDaddy i am a big Craig Harper fan. These studies are hard to do, and far from perfect. But this provides way more information (over 10 years of study) than someone saying “I fertilized an oak and it did great.”
TreeDaddy
5 year old buck +
All valid points
I will download paper and read materials, methods,statistical analysis ,etc
I am also a fan of Craig harper and love to read his work
I will, however, remain cautious and circumspect about extrapolating the recommendations of others in different ecoregions
bill
FarmerDan
5 year old buck +
It would be fantastic if you could inject a liquid fertilizer solution into the soil. Great of lawn and estate work but probably not so likely for habitat work.
It takes manpower.
A post hole digging iron....punch hole a foot apart. Start at the drip line and work in towards the trunk. If you can get 2/3 the distance from the drip line to the trunk stop. If you can make the hole a foot deep fill it with a cup of fertilizer. Cover the hole.
It takes manpower.
A post hole digging iron....punch hole a foot apart. Start at the drip line and work in towards the trunk. If you can get 2/3 the distance from the drip line to the trunk stop. If you can make the hole a foot deep fill it with a cup of fertilizer. Cover the hole.
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FWIW, On my property in NW Wisconsin I have tons of northern pin oak. They dont get real big and very rarely produce a good crop of acorns. In Dec 22 we had a heavy snow / ice event that broke trunks on many of the oaks. While cleaning up the mess last summer (2023) I noticed that the damaged trees had massive acorn production on the remaining parts of the trees.
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omicron1792
5 year old buck +
That’s cool to notice. Reminds me of the MSU deer lab work with mineral stumps. Mature tree leaves have very low nutrient content. Cut the tree down and let it resprout, and the new growth is full of minerals.
Angus 1895
5 year old buck +
I was reading about the culture of English walnuts. The article stated fertilizer would increase yield. Also growing legumes like alfalfa’s clovers near trees helped.
TreeDaddy
5 year old buck +
Telemark
5 year old buck +
I would tend to agree. It also doesn't mention there how they were able to both exclude animals from eating the acorns in order to measure increases in productivity while simultaneously monitoring depredation of acorns. And how many square meters were counted per tree? Which animals were eating the acorns? How was the area of the crown determined? Was the age of the trees considered? Was the data from the drought years thrown out or included? We're different kinds of fertilizer used? Was there a difference from site to site, or were the effects of treatment uniform across all locations?
omicron1792
5 year old buck +
The absence of all those variable controls doesn’t then mean the anecdotal evidence of fertilizer working is correct. It would mean the data strongly supports it not working with more robust studies needed. That will never be done because no money in doing another 15 year study.
Telemark
5 year old buck +
That's pretty much exactly my take on the whole thing except for the significance of the drought years. I suspect that drought can negate the effects of fertilizer, and I would be willing to bet money that in a series of two or three consecutive years, starting with the application of the fertilizer, there would be an increase in production and wildlife use of the fertilized trees if there was normal rainfall or supplemental watering of the trees.
That is to say, I do tend to take the researchers in this study at their word regarding their findings, but I think their results are incomplete, and I suspect the drought conditions were a significant factor in this particular study.
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Telemark
5 year old buck +
Well here's another issue I have with the study:
"We fertilized each tree in the fertilization treatments (F
and CRF treatments) with 168 kg/ha of actual nitrogen by applying
ammonium sulfate ((NH4)2SO4) around each tree. Application rates of
actual phosphorus (monocalcium phosphate; CaH4P2O8) and potassium
(potassium chloride; KCl) differed between sites and years based on soil
test results. We added enough phosphorus and potassium each year to
maintain 101 kg/ha of phosphorus and 269 kg/ha of potassium in the
soil (Savoy and Joines, 2009). We calculated the amount of fertilizer
needed for each tree by measuring the crown area (i.e., surface area
from the trunk of the tree to the edge of the crown) of each tree"
That sounds sloppy. It just adds a lot more variables. If they had added a single bag of triple 12 to each tree or each unit of area, I believe they would have gotten very different results. They applied the same amount of nitrogen to each tree but varied the P and K?
The more I read about this study the more skeptical I become of it.
"We fertilized each tree in the fertilization treatments (F
and CRF treatments) with 168 kg/ha of actual nitrogen by applying
ammonium sulfate ((NH4)2SO4) around each tree. Application rates of
actual phosphorus (monocalcium phosphate; CaH4P2O8) and potassium
(potassium chloride; KCl) differed between sites and years based on soil
test results. We added enough phosphorus and potassium each year to
maintain 101 kg/ha of phosphorus and 269 kg/ha of potassium in the
soil (Savoy and Joines, 2009). We calculated the amount of fertilizer
needed for each tree by measuring the crown area (i.e., surface area
from the trunk of the tree to the edge of the crown) of each tree"
That sounds sloppy. It just adds a lot more variables. If they had added a single bag of triple 12 to each tree or each unit of area, I believe they would have gotten very different results. They applied the same amount of nitrogen to each tree but varied the P and K?
The more I read about this study the more skeptical I become of it.
