Question
Located in Harlow Essex, Ground consists mainly of clay. We had a bitch dog for many years her urine killed of any turfs that I laid. The dog has gone but now the problem still exists. (after 2 years) There is a large amount of Moss which grows easily but any Turf laid dies of after about 6-9 months. Is there a cure or should I give in and slab the area. Turf used has been general meadow type from several different suppliers. Thanks in advance for any suggestions you may have. Reg Golder

Answer
>>"...the problem still exists..."

Many conditions and problems can affect turf grasses and lawn appearances. Without a more technical and direct close-up examination of your soil and lawn, the advice given here is based entirely upon the information provided and may or may not be the best remedy for your particular situation.

Note that a HIGH-CLAY soil is NOT A GOOD SOIL for growing turf-grasses.  This factor alone may be the cause of you lawn appearance problems. With persistent lawn appearance problems, improving the top-soil by adding soil amendments can often solve the problem.
  
Assuming there was a time in the history of your lot when turf-grasses could grow normally,... these are some facts and theories about your current lawn appearance problem as I understand it:

Dog urine contains UREA SALTS which will cause 'fertilizer burn syndrome' spots in healthy lawns.

When watered into a normal soil, the dog's urine can contribute to a green-healthy lawn. Unless the areas are well watered immediately after the dog urinates on the grass, they can cause hypertonic effects with the vegetation,...the burn syndrome.  With a typical soil, the microbes in the soil will bio-degrade the excess salty urine chemicals so the turf-grass can grow with no problems.  With a normal soil, dog urine will not be problem within a few weeks or months of Nature's metabolizing action in the soil and root-zone.  With time, rain and watering, a normal soil can compensate for the extra nitrates from dog effects. A high-clay soil will not have the normal microbes around to use excess biochemicals that can accumulate, and it is possible that the natural processes are therefore simply too slow.

 I suspect that your HIGH CLAY soil is deficient in any capacity to bio-degrade the fertilizing salts that have been deposited in the root-zone for all the years you had the dog around.  Your top-soil is therefore simply too salty for normal grasses to grow.  Some grass-types are more 'halide' or salt-tolerant than others.

I tend to think there are two possible practical remedies for your urine affected clayish top-soil IF indeed this is the main problem:

(01) USA a HARDY GRASS TYPE as a TEMPORARY HALIDE METABOLIZER to CORRECT the SOIL.

 A grass-type like BERMUDA GRASS might to able to prosper.  So you may want to try this grass-type at least for a while.  It is the most dog-urine resistant grass type there is and you can start it easily from seed after all danger of frost has passed.  In a few months, or in a couple of summers, it will sink its roots into your affected soil and (in theory) start to utilize all the urea salts that may remain.

I think Bermuda grasses, which are very popular in the USA, may be a rarity in your area, ...however, I can see no reason why this grass-type cannot be used.  After the salt-tolerant Bermuda has bio-degraded and utilized all the excess dog urine in the soil, you can eradicate the Bermuda and then go back to using the old-standard grass-types you may prefer.  You may, after a while, find that you like the Bermuda grass and can tend it to make a fine lawn.

Your local seed store may sell Bermuda grass by the ounce.  Perhaps you can purchase a small quantity and see if or not it will do OK.  Experiment with an area first before seeding the entire lawn. It is possible that the top-soil could be so very hypertonic that not even Bermuda grass can prosper,..so you do not want to go to a lot of effort without seeing if or not this is so.

Note that new grass seedlings cannot be allowed to dry-out, so to get any grass-type started from seed may require some effort to keep things well-hydrated. Wind and warm conditions can destroy all the tiny seedlings in a matter of hours.  But do not give up on Bermuda, buy some extra seed just in case there are losses due to weather conditions and not soil conditions.
Disperse the seed on cloudy days and during more humid-windless conditions to make the task easier.

Bermuda grasses are a warm-climate type which will become dormant in the cold winters.  It will re-vive in the spring.  Bermuda grasses are extremely hardy and are drought and disease resistant.  They need full-sun conditions.  With Bermuda grass, you will not have to mow or water the lawn all winter.  Do not fertilize the Bermuda grass to encourage it to utilize any and all residual doggy nitrogen salts in the soil.

Bermuda grass my be locally available, and if not, there are many mail-order suppliers.  Recommended are 'U3' or 'Arizona' Cultivars, these are very common grass-types in the USA.
A next-best choice grass-type you may consider is a TALL FESCUE grass-type.  Tall Fescues are more shade-tolerant than Bermuda grasses. 'Rembrandt' or 'Plantation' Tall Fescue are about the best cultivars of this grass-type. Fescues will grow all year and will not go dormant in the winter.

(02) REPLACE the TOXIC SOIL.

The only other alternative for you ...to get your lawn back to normal...  would be to actually excavate-away the toxic top-soil and dispose of it.  Then you can replace it with a better top-soil.  This may require a great deal of work.   It should involve the addition of up to 3-4 inches of quality soil which you can have trucked-in to your property.  If possible you should try to work this new soil into the clay base as much as possible.  This should do much to fix the salty-soil conditions and also help the high-clay scenario.  

A combination of remedies 1 and 2 above may provide more long-term curative effects for the salty soil. The second remedy is more labor-intesive and expensive, but should give the fastest and most certain best-results.  Again, I can not guarantee these remedies as fail safe, but the are logically good actions to consider.

If you have doubts about your top-soil chemistry or if any of the above remedies fail,...you may benefit from having your top-soil laboratory tested.  It should be tested for toxic salts, or 'total salinity' and for nitrate percent as well as pH (acidity). [Mosses tend to prosper with a highly acidic and 'low pH' top-soil.  Most turf-grasses also like a slightly acidic top-soil, but there is also a chance that your soil could be hyper-acidic for the grass-type you have been trying to grow.]
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With a good fertile-loamy well draining top-soil, best quality hybrid grass type(s), 1-3 inches of water per week, plenty of sun-light, ...almost anyone can have an excellent lawn with a minimum maintenance effort.
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I Hope this has answered your question(s)!

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