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Author: Subject: Brown dead patches in my lawn
wg48temp9
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[*] posted on 21-7-2022 at 01:11
Brown dead patches in my lawn


I have had a period of very hot weather where I live, actually the highest temperature ever recorded in this area

My lawn has developed several small (200mm) brown dead patches which I initially assumed was caused by the hot dry weather however the distribution was unusual.

I have two dogs who pee on my lawn which previously had not harmed the grass. What I think may be happening is during the hot spell the dogs urine is more concentrated than usual and due to the dry soil and high evaporation becomes concentrated.

My hypothesis is the small brown patch of grass are caused by my dogs urine.

[Edited on 7/22/2022 by wg48temp9]




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[*] posted on 21-7-2022 at 01:22


Could easily be dog pee.
And it would not need to be unusually concentrated. Very dry soil and quick evaporation would have the same effect.

The same thing happens in summer here with my lawn and dog.
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Morgan
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[*] posted on 21-7-2022 at 05:05


I remember seeing a few gardening programs on TV about the topic.
https://www.puppyleaks.com/female-dogs-dead-grass/
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Rainwater
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[*] posted on 21-7-2022 at 17:35


A ph test of the soil could reveal important information.
Lawn plants are less tolerant of ph extremes when they are under stress.




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[*] posted on 22-7-2022 at 01:24


Yes I am aware that the advice is don't let your bitch pee on the lawn. I ignored it because in the past (>ten years) there was only an occasional or no brown patches.


Quote: Originally posted by Rainwater  
A ph test of the soil could reveal important information.
Lawn plants are less tolerant of ph extremes when they are under stress.


I do want to test the ph of the soil around my acid loving Rhododendrons. I could check the few spots on the lawn at the same time.

There is building rubble mixed in with the soil in most places in the garden that I have dug a hole for a plant. Two of my rhododendrons don't look very well and are growing slowly even after putting ferrous sulphate and and sulphur on the soil in an attempt to lower the ph.

I do have some universal and narrow range ph paper but how do a get a representative sample of the soil for the ph test? I guess I will have to sample at several places around the Rhododendrons.

I should add that the occasional brown patch is caused by spilling petrol when I fill up the motor mower.

[Edited on 7/22/2022 by wg48temp9]




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[*] posted on 22-7-2022 at 01:59


When i test mine i take 4 samples from around the plant from 2in under the top. With a 1/2in piece of steel pipe. About a tablespoon each. Put them all together

In a 50ml beaker i add enough water to just cover the samples. Cover and shake. Repeat until the dirt starts to seperate into layers. If a top aqueous layer is not present. Add a little more water then repeat.
Let everything settle for a few minutes.
Idealy you want 10%~20% sand. 10% clay 30~50% organic and the rest water. Ph test the water.




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[*] posted on 22-7-2022 at 02:00


From my experience the dog wee left brown spots only during hot and dry periods. If i saw her wee i just hosed the spot and it was fine.

Here in Australia they sell rocks for the dogs water bowl that supposedly stops the wee killing the lawn. I never tried it.
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[*] posted on 22-7-2022 at 03:12


The standard industry pH field test for soil calls for a 1:5 slurry of soil to dH2O.
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[*] posted on 27-7-2022 at 15:39
Mammals


All mammals and some others outside the definition produce urea that is present
in the urine. Urea is high nitrogen, about 46.6%. The only thing I've come up
with higher is anhydrous ammonia at almost 82%. Sounds like the lawn or
anything around is being "burned" by an excess of nitrogen. No surprise.
BTW, watering the spots, where the dog squirts, can lower the nitrogen load.




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Morgan
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[*] posted on 28-7-2022 at 09:48


Some of the other chemicals in urine might not be what the grass likes either, or in too concentrated a form and synergistic with the nitrogen. Plants probably don't like a lot of things that interfere with normality to function properly.
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AJKOER
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[*] posted on 31-7-2022 at 11:21


Some literature on dog urine impacts, to quote from "Dog Urine Has Acute Impacts on Soil Chemistry in Urban Greenspaces" at https://www.frontiersin.org/articles/10.3389/fevo.2020.61597... , to quote:

"The urine of dogs is high in nitrogen (N) and may represent a significant portion of the annual urban N load. We examined the spatial distribution and impact of N deposition from dog urine on soils in three urban greenspace typologies in Finland: Parks, Tree Alleys, and Remnant Forests. We analyzed soil from around trees, lampposts and lawn areas near walking paths, and compared these to soils from lawn areas 8 m away from pathways. Soil nitrate, ammonium, total N concentrations, and electrical conductivity were significantly higher and soil pH significantly lower near path-side trees and poles relative to the 8 m lawn plots. Also, stable isotope analysis indicates that the primary source of path-side N are distinct from those of the 8 m lawn plots, supporting our hypothesis that dogs are a significant source of N in urban greenspaces...."

Also, my photochemistry related comment, nitrates are photocatalyst. The active electron holes (h+, see discussion here https://www.sciencedirect.com/topics/earth-and-planetary-sci... ) formed in light can remove the OH- (from H2O = H+ + OH-) creating the active .OH radical per the reaction:

h+ + OH- -> .OH

where .OH can attack organic DNA. Note, the H+ largely remains thereby lowering pH into more acidic levels.

Also, the reported rise in "electrical conductivity" implies more efficient galvanic and Galvano-Fenton (and Fenton-like) reactions, further increasing radical activity.

Bottom line, the dog adds to pathways based on increased solar activity from photoactive nitrates changing soil chemistry (low pH) and even directly attacking organic DNA resulting in lost of grass.

[Edited on 31-7-2022 by AJKOER]
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[*] posted on 31-7-2022 at 11:58


And the occasional drug the dog may be given ...some dogs getting medicated daily or such for certain conditions ....
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