Fate and transport of nitrogen applied to six warm-season turfgrasses

A greenhouse study compared six warm season turfgrasses [common bermudagrass [Cynodon dactylon (L.) Pers.], `Tifway' hybrid bermudagrass (C. dactylon X transvaalensis), centipedegrass (Eremochloa ophiuroides (Munro) Hack.), `Raleigh' St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze], `Meyer' zoysiagrass (Zoysia japonica Steud.), and `Emerald' zoysiagrass (Z. japonica X tenuifolia)] for N[O.sub.3]-N leaching and N use efficiency. Sod was established in sand-filled columns and managed under worst-case conditions to promote nitrate leaching. Ammonium nitrate was applied at 50 kg N [ha.sup.-1] on seven dates, with the final application labeled with [sup.15]N. Leachate samples were collected and analyzed for N[O.sub.3]-N and N[H.sub.4]-N and clippings were analyzed for total N. Leaching losses were high following the first N application, ranging from 48 to 100% of the N[O.sub.3]-N and 4 to 16% of the N[H.sub.4]-N applied. Nitrate loss from subsequent applications was reduced substantially, while N[H.sub.4] leaching was essentially eliminated. There were significant differences among species for leachate N[O.sub.3]-N concentration and cumulative N leached, with St. Augustinegrass being the most effective and Meyer zoysiagrass the least effective at minimizing N[O.sub.3] leaching. Nitrogen recovery by the turf ranged from 63% for Meyer zoysiagrass to 84% for hybrid bermudagrass. Root length density (RLD) varied significantly among species at depths >30 cm, and was negatively correlated with N[O.sub.3] leaching loss. These results document differences between the warm season turfgrasses for N[O.sub.3] leaching potential, possibly related to root distribution, and emphasize that species selection is an important factor in minimizing environmental impacts from turfgrass management.