Translate the following English sentence to French:
"The main problem here was that, because of the extremely high density of livestock in many parts of the Union, keeping to within the limit of 170 kg of nitrogen per hectare of farmland caused immense difficulties with the production of farm manure in several countries."
Le principal problème à cet égard est que l' augmentation du bétail dans de nombreuses régions de l' Union a rendu difficile le respect de la limite de 170 kg d' azote par hectare de surface cultivable lors de l' épandage d' engrais économiques.