Understanding the determinants of nitrate leaching should improve nitrogen uptake efficiency and reduce ground water contamination. This column lysimeter study examined the effect of root architecture on NO3 leaching from two genotypes of creeping bentgrass (Agrostis palustris Huds.) differing in rooting characteristics. Ammonium nitrate was applied (50 kg N ha−1) and the columns were irrigated with 1, 2 or 3 cm day−1 (Exp. 1) or irrigation was delayed 1, 3 or 5 d (Exp. 2). In Exp. 1, leachate NO3 concentrations and total N leached from the shallow‐rooted (SR) genotype were approximately twice those from the deep‐rooted (DR) genotype. An average of 38 and 18% of the applied N leached from the SR and DR genotypes, respectively. Cumulative leaching losses increased with irrigation depth. In Exp. 2, NO3 leaching was reduced 90% or more by increasing the time period for immobilization from 1 to 5 d. Recovery of applied 15N in the tissue averaged 87% after 2 mo. Absorption of NO3 and NH4 was measured in nutrient solution culture. The SR genotype had significantly higher uptake rates than DR for both forms of N, expressed on a root weight basis. Collectively these data indicate that a deep‐rooted turfgrass absorbs N more efficiently than a shallowrooted turf, reducing the concentration and total amount of NO3 leached. The effect is apparently not due to differences in N uptake, but rather to rooting patterns. Environmental conditions and management practices that affect rooting depth and density may thus affect N nutrition and NO3 leaching.

A tentative alluvial sequence of Hay Hollow Valley 2. Correlation coefficients, r and rho, of the total numbers of plants by species by microhabitats 3. Correlation coefficients, r, of numbers of plants by species by microhabitats using mean data 4. Correlation coefficients, r and rho, of animal densities by microhabitat ... 5. Total plant distribution for all quadrats by microhabitat 6. Total animal transect data 7. Total animal transect data by density per square mile 8. Burial information chart 9. Partial behavioral chain of maize for the Hopi, circa A.D. 1900 10. Tabulation of room floor areas, and wall and roof openings, Joint Site Pueblo 11. List of tree-ring dates from the Joint Site and their proveniences I.

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A greenhouse study compared six warm season turfgrasses {common bermudagrass [Cynodon dactylon (L.) Pers.], ‘Tifway’ hybrid bermudagrass (C. dactylon × transvaalensis), centipedegrass (Eremochloa ophiuroides (Munro) Hack.), ‘Raleigh’ St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze], ‘Meyer’ zoysiagrass (Zoysia japonica Steud.), and ‘Emerald’ zoysiagrass (Z. japonica × tenuifolia)] for NO3‐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−1 on seven dates, with the final application labeled with 15N. Leachate samples were collected and analyzed for NO3‐N and NH4‐N and clippings were analyzed for total N. Leaching losses were high following the first N application, ranging from 48 to 100% of the NO3‐N and 4 to 16% of the NH4‐N applied. Nitrate loss from subsequent applications was reduced substantially, while NH4 leaching was essentially eliminated. There were significant differences among species for leachate NO3‐N concentration and cumulative N leached, with St. Augustinegrass being the most effective and Meyer zoysiagrass the least effective at minimizing NO3 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 NO3 leaching loss. These results document differences between the warm season turfgrasses for NO3 leaching potential, possibly related to root distribution, and emphasize that species selection is an important factor in minimizing environmental impacts from turfgrass management.

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