Temporal data on aboveground biomass and nutrient uptake by species and functionally diverse native perennial plant species and communities is needed to enhance the performance of in-field buffer conservation practices. Comparisons on the performance of monocultures and polycultures of four native perennial prairie species having different functional traits (e.g., forb, grass, nitrogen-fixer) relative to monocultures of corn soybean, brome, and switchgrass were conducted in terms of aboveground biomass production and N & P uptake at peak performance, at the beginning and end of the growing season, and over the course of the whole year. Data collection occurred in 2006, a year after plots were established. Our findings show that the polyculture treatments did not outperform their component species in monoculture for peak values of aboveground biomass and N and P uptake. This was the opposite of what was expected. However, the polyculture treatment with the highest diversity did exhibit the greatest relative aboveground net primary productivity. The perennial species, particularly the C3 species, had higher biomass production and nutrient uptake at the beginning and end of the growing season compared to annual crops. The species stiff goldenrod was one species that performed as well as Corn for peak aboveground biomass and nutrient uptake. These results suggest that high diversity plant communities may potentially be the best chose for use in in-field buffer conservation practices when production and nutrient uptake at the beginning and end of the growing season as well as over the course of the year are wanted. High yielding monocultures could be good when considering high performance at a single mid summer point in the growing season, however, having multiple species that can accomplish these same functions would be beneficial in the long run should some species (like Stiff Goldenrod) fluctuate in productivity from year to year (Camill et al., 2004).