Comparison of nitrogen use by two population densities of eastern black nightshade (Solanum ptycanthum)

Greenhouse hydroponic and field experiments were conducted to determine the effect of nitrogen (N) fertilizer on eastern black nightshade growth and N content. After 4 wk in hydroponics, the greatest shoot dry mass occurred in the 5 or 10 mM nitrate treatments. An exponential model was strongly correlated with eastern black nightshade root and shoot growth in the 5 or 10 mM nitrate treatments. Eastern black nightshade reached the exponential stage of growth approximately 21 d after transfer to the nitrate treatments. Root dry mass was only 10% of shoot biomass. There was a substantial increase in height and growth rate when plants were fertilized with 168 kg N ha^-1. Eastern black nightshade was at its maximum growth 12 wk after planting, and fresh mass increased with N up to 336 kg N ha^-1, the greatest N concentration in the study. The greatest N content was in the upper leaves and the least in the lower stem. These results indicate that eastern black nightshade growth is favored by high rates of N.