The Effect of Nitrogen Availability on the Growth and Cover of the Myriophyllum spicatum

Myriophyllum spicatum L., a species able to grow in wide range of ecological conditions, was evaluated for its requirements for nitrogen both in controlled and natural conditions. In controlled conditions, the growth rate of the plants rise with increasing nitrate application. The optimal dosage of ammonium supplementation tended to be between 10-100 mu M, higher levels were restrictive. High levels of ammonia but also nitrate, over 32 mu M, were found to be unfavorable for the cover of M. spicatum, in water bodies in Slovakia. However, in controlled conditions, such a suppressive effect was confirmed only for ammonia but not for nitrate. Other nitrate related factor that could lead to restrictions in coverage of this species in natural habitats is water turbidity that was found to be ever high in nitrate rich water bodies. The results have also shown that M. spicatum has not a clear preference to the form of available nitrogen, though may somewhat prefer mixed nitrogen supply.