Various fertilizers differ in toxicity. Ammonium nitrate, monoammonium phosphate and ammonium sulphate are similar in toxicity and much safer than anhydrous ammonia, aqua ammonia or urea. Diammonium phosphate is more toxic than monoammonium phosphate but less toxic than urea. More care should be taken, particularly with sensitive seeds such as beans or peas, and on coarse-textured soil (sand and sandy loam), than is required with ammonium nitrate or monoammonium phosphate.
Because anhydrous ammonia and aqua ammonia are extremely toxic fertilizers, they should not be placed near seeds. It is preferable to make preplant applications crossways to the direction in which the crop will be planted. Stand reductions may still occur over the band in very dry soils or if planting takes place too soon after application.
Urea is toxic when banded with or near the seed but is safe when broadcast at rates normally used.
Information courtesy of the Ontario Ministry of Agriculture, Food, and Rural Affairs