Nitrogen fertilization increases diversity and productivity of prairie communities used for bioenergy

Abstract

Using prairie biomass as a renewable source of energy may constitute an important opportunity to improve the environmental sustainability of managed land. To date, assessments of the feasibility of using prairies for bioenergy production have focused on marginal areas with low yield potential. Growing prairies on more fertile soil or with moderate levels of fertilization may be an effective means of increasing yields, but increased fertility often reduces plant community diversity. At a fertile site in central Iowa with high production potential, we tested the hypothesis that nitrogen fertilization would increase aboveground biomass production but would decrease diversity of prairies sown and managed for bioenergy production. Over a 3 year period (years 2-4 after seeding), we measured aboveground biomass after plant senescence and species and functional-group diversity in June and August for multispecies mixtures of prairie plants that received no fertilizer or 84 kg N ha À1 year À1 .We found that nitrogen fertilization increased aboveground biomass production, but with or without fertilization, the prairies produced a substantial amount of biomass: averaging (±SE) 12.2 ± 1.3 and 9.1 ± 1.0 Mg ha À1 in fertilized and unfertilized prairies, respectively. Unfertilized prairies had higher species diversity in June, whereas fertilized prairies had higher species diversity in August at the end of the study period. Functionalgroup diversity was almost always higher in fertilized prairies. Composition of unfertilized prairies was characterized by native C 4 grasses and legumes, whereas fertilized prairies were characterized by native C 3 grasses and forbs. Although most research has found that nitrogen fertilization reduces prairie diversity, our results indicate that early-spring nitrogen fertilization, when used with a postsenescence annual harvest, may increase prairie diversity. Managing prairies for bioenergy production, including the judicious use of fertilization, may be an effective means of increasing the amount of saleable products from managed lands while potentially increasing plant diversity.

Spatial and Temporal Dynamics of Soil‐Surface Carbon Dioxide Emissions in Bioenergy Corn Rotations and Reconstructed Prairies

“…4). As will be noted in the following sections, this effect is associated with lower soil T soil when prairies received N fertilization and stimulated fuller plant canopies ( Jarchow and Liebman, 2013). Additionally, Jarchow and Liebman (2013) reported that the fertilized and unfertilized prairies at the same field sites were dominated by native C 3 and C 4 plants, respectively.…”

“…As will be noted in the following sections, this effect is associated with lower soil T soil when prairies received N fertilization and stimulated fuller plant canopies ( Jarchow and Liebman, 2013). Additionally, Jarchow and Liebman (2013) reported that the fertilized and unfertilized prairies at the same field sites were dominated by native C 3 and C 4 plants, respectively. They also reported that fertilized prairies had greater diversity of plant species in August, whereas unfertilized prairies had greater diversity in June ( Jarchow and Liebman, 2013).…”

“…5). This is attributed to the higher quantity of vegetative biomass in the crop canopy intercepting solar radiation (Jarchow and Liebman, 2013;Jarchow et al, 2012;Morris, 1989). Among the continuous corn systems, CCW was significantly lower in T soil than CC on only 5 of the 47 sample dates (i.e., 11%) with most occurrences during May.…”

“…Additionally, Jarchow and Liebman (2013) reported that the fertilized and unfertilized prairies at the same field sites were dominated by native C 3 and C 4 plants, respectively. They also reported that fertilized prairies had greater diversity of plant species in August, whereas unfertilized prairies had greater diversity in June ( Jarchow and Liebman, 2013). As expected, one or both prairies were significantly greater than one or more row crops on 42 of the 64 sampling dates (i.e., 66%).…”

Diversifying Agricultural Catchments by Incorporating Tallgrass Prairie Buffer Strips

“…For example, Rothrock and Squiers (2003) found that N fertilized prairie communities remained dominated by annual weeds and did not shift to perennial species. Alternatively, Jarchow and Liebman (2012) found that spring fertilization of prairies increased late season prairie species diversity and did not encourage exotic species.…”