EFFECT OF NITROGEN AND PHOSPHORUS ON GROWTH AND INTERFERENCE BETWEEN BROMUS-TECTORUM AND TAENIATHERUM-ASPERUM

The effects of nitrogen and phosphorus supply on growth and interferen ce between Bromus tectorum and Taeniatherum asperum were studied in gr eenhouse sand culture, using a modified replacement series experiment. Three levels of N and P were applied in all possible combinations. He ight, number of leaves and biomass production were reduced in both spe cies in response to nutrient reduction. B. tectorum had higher dry mat ter production than T. asperum at high nitrogen or phosphorus concentr ations' or when both nutrients were present. When either nutrient was lacking, yield of both species was similarly reduced. Nitrogen deficie ncy was more influential on yield reduction than phosphorus in both sp ecies. In mixtures, B. tectorum was highly competitive at high concent rations of N and P. At lower levels of N and P supply, the species per formed equally. Early patterns of resource allocation and high growth rates in B. tectorum enable that species to outperform T. asperum at h igh nutrient concentration. These advantages were reduced by nutrient deficiency, which led to competitive equality between the species.