Early uptake of 15N in shortgrass prairie

The early uptake ¹⁵N fertilizer in grassland was monitored by means of destructive samplings during the first two weeks after application. The predominantly litter compartments (aboveground dead, senescent and detrital roots) accounted for two-thirds of the ¹⁵N immobilization in plant parts in the first few hours after fertilization. This uptake is believed due partly to adsorption and partly to immobilization by the microorganisms associated with senescent and detrital plant parts. By 14 days, green tops and crowns accounted for 72%; live roots, 7%; and the aboveground dead and senescent and detrital roots, 21% of the total ¹⁵N uptake by the plant materials. The distribution of applied ¹⁵N between live and litter compartments was not significantly affected by rate of application.