Production of organic matter and interference of two grasses at different levels of nitrogen supply

Arrhenatherum elatius (Oatgrass) and Bromus erectus (Bromegrass) were grown for two years in pots in pure and mixed stands (total competition) with three levels of nitrogen supply. There was one harvest in the first year and one final harvest of shoots and roots in the second year. Plant height, proportion of flowering stands, and fresh and dry weight were measured. The plant material was analysed for protein and soluble nitrogen, for total ash, total lipids and carbon.

In both grasses, additional nitrogen supply resulted in greater biomass, shoot length, proportion of flowering stands and nitrogen content, but Oatgrass was able to use the nitrogen more effectively than Bromegrass.

In mixed stands both shoot biomass and the shoot/root ratio of Oatgrass were increased compared with pure stands. This increase was greater in the second than in the first year. In the first year Oatgrass showed a higher nitrogen content under competition, but this was true for Bromegrass in the second year. The differences between the years appear to be mostly due to the different developmental stages of the plants.

It was concluded that nitrogen supply is effective in regulating the distribution of Oatgrass and Bromegrass. Nitrogen seems to be of greater importance than water for which experimental results were reported in an earlier paper (Salinger and Bornkamm, 1982).