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 interference between Bromus tectorum and Taeniatherum asperum were studied in greenhouse sand culture, using a modified replacement series experiment. Three levels of N and P were applied in all possible combinations. Height, number of leaves and biomass production were reduced in both species in response to nutrient reduction. B. tectorum had higher dry matter production than T. asperum at high nitrogen or phosphorus concentrations' or when both nutrients were present. When either nutrient was lacking, yield of both species was similarly reduced. Nitrogen deficiency was more influential on yield reduction than phosphorus in both species. In mixtures, B. tectorum was highly competitive at high concentrations of N and P. At lower levels of N and P supply, the species performed equally. Early patterns of resource allocation and high growth rates in B. tectorum enable that species to outperform T. asperum at high nutrient concentration. These advantages were reduced by nutrient deficiency, which led to competitive equality between the species.