Reactive Nitrogen in Turfgrass Systems: Relations to Soil Physical, Chemical, and Biological Properties

Abstract

Turfgrass systems contribute to the loading of reactive N to water and air via runoff, leaching, and gas emission. Yet, a comprehensive approach has never been developed to assess N loss potential from turfgrass systems. We used pools and production of reactive N (inorganic N, extractable organic N, and NO) to estimate N loss potential and hypothesized that this potential could be predicated by basic soil properties. A total of 68 soil samples were taken from 17 bermudagrass sites in North Carolina. Basic soil properties were analyzed, including soil C and N, C:N ratio, microbial biomass, moisture, pH, and percent silt/clay/sand. Soil samples varied most widely in texture, followed by soil C and N, microbial biomass, moisture, pH, and C:N ratio. The pools of extractable organic N and inorganic N were comparable, indicating that soluble organic N should be considered as a pathway of N loss from turfgrass. Turfgrass with large pools and production of reactive N was characterized by high soil C and N, microbial biomass, and moisture. Because soil C and N accumulate over time after turfgrass establishment, turfgrass age could be a suitable practical indicator of N loss potential and thus could be used to implement changes in management. Pools and production of reactive N in liquid and gas phases were well correlated, suggesting that if a turfgrass system has a high potential of N loss via leaching and runoff, it may also be of a high potential for NO emissions.

The extent and pathways of nitrogen loss in turfgrass systems: Age impacts

“…We used intact soil cores in this study to investigate reactive N loss from turfgrass ecosystems and found a cup-shaped pattern of reactive N loss vs. time. This differs from data obtained using sieved and thoroughly mixed soils (Lu et al, 2015) where reactive N (i.e., soil dissolved organic N, inorganic N and N 2 O-N) increased with soil organic C and N, suggesting a positive relationship between reactive N loss and turfgrass age. Such discrepancy may be due to their experiment conditions favoring enzyme and microbial activity and therefore intensifying enzyme and microbial activity-mediated production of soluble N. When vegetation was included, as in the present study, microbial turnover and growth efficiency might play more important roles in regulating soluble N (Blagodatskaya et al, 2014;Cheng, 2009;Schmidt et al, 2007).…”

“…A 22-month lysimeter study showed that 25 to 78% of N leached from a turfgrass system was in the organic form (Barton et al, 2009). By examining 17 bermudagrass systems, Lu et al (2015) also showed that water-and salt solution-extractable soil organic N was comparable to soil inorganic N, implying that N leaching or runoff via organic form could be as high as inorganic species.…”

Nitrous Oxide Emissions from Turfgrass Receiving Different Irrigation Amounts and Nitrogen Fertilizer Forms

“…When pooled over the entire 2‐yr study, correlations between daily N 2 O‐N fluxes and WFPS were weak but significant ( r = 0.23, P < 0.001, n = 2484). In past research, higher N 2 O fluxes have been associated with higher soil water content (Denmead et al, 1979; Mosier and Hutchinson 1981; Ryden, 1981; Bremer, 2006; Bijoor et al, 2008; Lewis and Bremer, 2013; Lu et al, 2015). However, others have reported that higher WFPS did not always enhance N 2 O production in turf systems (Townsend‐Small et al, 2011; Li et al, 2013).…”

“…An elevated soil water content, also referred to as water-filled pore space (WFPS), during or after N fertilization may be a key driver in amplified N 2 O fluxes. Past N 2 O research in turf has shown that N 2 O emissions typically increase after N fertilizer applications and precipitation or irrigation (Bremer, 2006;Bijoor et al, 2008;Lewis, 2010;Lewis and Bremer, 2013;Lu et al, 2015). Further research is required on the effects of irrigation quantity or frequency on N 2 O fluxes in turfgrass.…”

Composition of nitrogen in urban residential stormwater runoff: Concentrations, loads, and source characterization of nitrate and organic nitrogen

“…Urbanization and anthropogenic activities have accelerated nutrient enrichment and water quality problems in urban waters [1,2]. Nitrogen (N) is often a limiting nutrient in coastal waters [3][4][5], where excess N loading can lead to cultural eutrophication and algal proliferation [6].…”