**6.1.4 Competitive ability of energy grass on weeds**

The competitive ability of energy grass crop can be demonstrated using experimental plot data. A strong linear relationship was found between the biomass production and the logarithmic values of total weed cover suggesting a high competitive ability of the crop. With less then 10 t/ha of biomass dry yield the cover of weeds exceeded 50 %, while at 15 t/ha the value decreased to 20-25 % and to 2-5 % at 20 t/ha.

*Elymus elongatus* is a rare, native plant species in Hungary; therefore its agricultural production is much more favourable than other exotic biomass grasses (e.g. *Miscanthus* × *giganteus, Sorghum bicolor*). Since its stands require a certain weed control only in the year of establishment, chemical input into the environment decreases significantly compared to other intensive cultures. Under favourable conditions, energy grass can entirely close its canopy and exclude more weed species or considerably decrease their cover by the third year of cultivation. This remarkable competitive ability of a crop is appreciated by farmers as it decreases the demand of herbicide use as well as the costs of the agricultural production.
