Mercury retards plant growth.

[anut]

This is a fact. This is not a speculation:

Mercury-induced changes in growth variables and antioxidative enzyme activities in Indian mustard - Journal of Plant Interactions

[anut]

Excrement from humans or other non-vegetarian animals contain mercury. I would recommend against fertilizing vegetables with human urine.

Also, lime contains mercuric compounds. According to my experiments, the mercury toxicity from lime is not as negligible as many people believe. I originally thought the PH value of lime is the main factor contributing to the problem. But after correcting the soil PH with acidic fertilizers, my plants still grew as slowly as they used to.