We measured nitrogen content of plant parts, seed yield, and plant mass of four species of spring annual plants grown under different water and soil nitrogen conditions. We hypothesized that nitrogen would have little effect or a detrimental effect of the nitrogen-fixing legume A. nuttallianus. We hypothesized that water would have the greatest effect of the species of annuals that exhibit little or no growth response to soil nitrogen availability (E. diffusum and E. nuttallianus). Plant tissue nitrogen and seed production were hypothesized to increase in the nitrogen fertilizer-responsive species. L. lasiocarpum and C. stevioides.