| Attempts to reestablish native grasses in regions occupied by alien annual grasses often fail, due to the superior competitiveness of the annuals, particularly in high nitrogen (N) soils. This experiment tested whether straw, a recalcitrant soil amendment, could reduce available soil N and thereby suppress the annual grass Avena fatua (wild oat) while leaving unaffected the native perennial Nassella pulchra (purple needlegrass). Avena fatua and Nassella pulchra were planted separately and together in 60 cm-deep pots, with four different amounts of straw incorporated into a native high-N loam soil. After harvest, shoot and root biomass and nitrogen content were measured. Soils were analyzed for total N, mineralizable N, nitrate, and ammonium. Experimental results indicate that Avena fatua is more sensitive, and Nassella pulchra is relatively insensitive, to lower available soil N resulting from the straw amendment. Straw therefore may be useful as a soil amendment in field-scale perennial grass seedings. |
