my father used 2 different lots of horse manure one lot perfect results and the other leaves all curled up etc.he was told that the horse manure had to many nitrates how can he solve this problem

i am hoping the manure is OLD as opposed to new as this will burn the plants with the acidity of the liquid.

I asked my Dad recently. He's a retired horticulturalist with 50 years experience in horticulture. He said there are other things in it also like amonia.

i am also an horticulturist and thats what i meant by acidity in the liquid.

I agree with Stevebuk - its possible that one lot of manure wasn't composted enough, and that would cause problems in the soil. If he can't remove it because it's been dug in, the only thing he can do is keep watering it a lot in the hopes of washing out the worst of it deeper into the soil.

There has also been an issue highlighted in the press recently of residual pesticides in horse manure. Even that which has been well rotted.

Gosh ! and I use horse manure in all sorts of ways ! I dig it in ,I mix it with the bought compost to bring on my young plants ,both flowers and all the veg,and then I make liquid manure to feed everything.
My toms and all other veg seem to be thriving,both inside the greenhouse and in the garden. I was not aware that it could cause a problem !!!
I use only the old manure most of the time but I have dug in fresh manure in the winter.

I'm sorry, I meant to say residual herbicides not pesticides in manure are causing problems with crops and garden plants.