NITRATE AND PHOSPHATE-UPTAKE BY AGROPYRON DESERTORUM AND ARTEMISIA-TRIDENTATA FROM SOIL PATCHES WITH BALANCED AND UNBALANCED NITRATE AND PHOSPHATE SUPPLY

To test the ability of plants to integrate small-scale imbalances in s oil nitrate and phosphate patches, plant growth and acquisition of nit rate and phosphate were measured for the perennial grass Agropyron des ertorum (Fisch. ex Link) Schult. and the shrub Artemisia tridentata Nu tt. ssp. vaseyana (Rydb.) Beetle in soil where the principal supply of nitrate and phosphate came from two enriched patches. The soil was ca lcareous loamy-skeletal Typic Haploxerolls. These patches were applied in two treatments: either nitrate and phosphate were applied in both patches (balanced treatment) or one patch contained only nitrate and t he other only phosphate (unbalanced treatment). The same total quantit y of nutrients was applied in both treatments and these included N-15 and P-32 tracers. The plants were in large pots in open field conditio ns. There were no significant differences in total biomass production and nitrogen concentration between the two treatments, indicating that both species had the physiological ability to integrate soil nutrient resources. Artemisia was able to acquire more phosphate in the unbala nced treatment, probably due to the high local solution phosphate conc entration. Generally Artemisia acquired more N and P than did Agropyro n.