Fate and Management of Turfgrass Chemicals - American Chemical

Chapter 10

The Effect of Salinity on Nitrate Leaching from Tall Fescue Turfgrass D. C. Bowman , D. A. Devitt , and W. W. Miller

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 9, 2018 | https://pubs.acs.org Publication Date: December 29, 1999 | doi: 10.1021/bk-2000-0743.ch010

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Department of Crop Science, North Carolina State University, Raleigh, NC 27695 Department of Environmental and Resource Science, University of Nevada, Reno, ΝV 89512 2

A column study was conducted to determine the impact of saline irrigation water on N 0 leaching from turfgrass. Tall fescue turf was grown in columns filled with sand and outfitted with a vacuum drainage system. Treatments consisted of three Ν levels (25, 50 and 75 kg N H N O - N ha month ) and three irrigation salinity levels (0, 1.5 and 3 dS m ) in a 3 X 3 factorial arrangement. Irrigation was scheduled to provide a 30% leaching fraction. Leachate was collected quantitatively after every irrigation and analyzed for salts and N O - N . Clippings were collected and analyzed for total N . Nitrate concentrations in the leachate were very low, averaging approximately 1.0 mg Ν L . Clipping yield and Ν content were unaffected by salinity, while root mass was increased. These data indicate that moderate levels of rootzone salinity do not increase NO leaching, nor do they impair growth or Ν absorption. This suggests that moderately saline irrigation water may be used to irrigate tall fescue turf without increasing NO contamination of groundwaters, as long as leaching is adequate to control rootzone salinity 3

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Soil salinity is a significant problem in the western United States. This is primarily due to the natural occurrence of soluble salts in many desert soils and the use of moderately saline water for irrigation. In southern Nevada's Las Vegas Valley, irrigation in excess of plant water requirement has leached native salts below the rootzone, creating a perched saline aquifer with an electroconductivity (EC) of approximately 9 dS m" and a volume estimated at approximately 100,000 acre feet/ If properly managed, this water supply could be used as an alternative or supplemental irrigation source, decreasing the demand on high-quality water while reducing the potential for contaminating the primary aquifer. One concern regarding the use of saline water for turf irrigation is the possible negative impact on turfgrass Ν nutrition. Nitrogen is the most heavily used nutrient in turfgrass management, with typical applications ranging from 50 to 600 1

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© 2000 American Chemical Society

Clark and Kenna; Fate and Management of Turfgrass Chemicals ACS Symposium Series; American Chemical Society: Washington, DC, 1999.

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kg Ν ha" yr" . When application rate exceeds turfgrass demand, excess Ν may be lost from the soil, becoming free to interact with other segments of the biosphere. In the arid southwest, and in southern Nevada in particular, it is essential that irrigation exceed évapotranspiration to facilitate leaching and maintain a favorable salt balance within the soil profile. However, this same downward movement of water becomes a prime pathway for nitrogen loss, as N 0 is highly mobile and subject to leaching. Work by Devitt et al. (1) and Letey et al. (2) on agricultural crops indicates that mass emission of nitrogen is more closely related to the amount of percolating water than to the amount of fertilizer applied. Since salinity reportedly inhibits Ν uptake in a number of species (J-5), leaching losses from turfgrasses could be increased considerably where saline irrigation waters are used in excess of evapotranspirational demand. Although no data are available on the effects of salinity on N 0 leaching, numerous studies have examined other factors and management practices as they affect N 0 leaching from turfgrasses. For example, Brown et al. (6) measured concentrations of N 0 as high as 74 mg Ν L* in the leachate below bermudagrass following application of 163 kg Ν ha" as N H N 0 , with total leaching loss of 23% of the applied N . Snyder et al. (7) found peak N 0 - N concentrations between 20 and 40 mg Ν L" in the soil solution below the turf rootzone 5 to 10 days after applying 50 kg Ν ha' as N H N 0 . Up to 56% of the applied Ν was lost during a 3 week period. However, minimizing the downward movement of water by carefully controlling irrigation with tensiometers reduced losses from 56% to 2% (8). Similar results have been reported by Morton et al. (P). De Nobili et al. (10) applied urea at a rate of 160 kg Ν ha" preplant to a turfgrass mixture and measured N 0 leaching over a four month period. Total leaching losses amounted to 9.5% of the applied N , with an average leachate concentration of 13 mg Ν L* . Cohen et al. (11) monitored N 0 - N in wells at four golf courses on Cape Cod over a two year period. At three of the four courses, N 0 concentrations in the shallow groundwater was only slightly higher than background. In contrast to the above studies, Rieke and Ellis (12) found little effect of fertilization on N 0 leaching following application of 290 kg Ν ha" yr" to a mixed turf. Starr and Deroo (13) reported similar low leaching losses. Mancino and Troll (14) investigated N 0 leaching from a creeping bentgrass turf under conditions favoring heavy leaching losses (sand rootzone, soluble nitrate-based fertilizers, and 46% leaching fraction). When the fertilizers were applied at a low rate of 9.76 kg Ν ha" weekly, N 0 leaching averaged less than 0.5% of the applied nitrogen. With a heavier application of 49 kg Ν ha* , cumulative losses averaged 3.5% for the N 0 sources. Gold et al. (15) reported a maximum flow-rated N 0 - N concentration of 1.62 mg Ν L" in the leachate from a home lawn fertilized with 244 kg Ν ha' yr" . Approximately half of the leachate samples had concentrations at or below 0.1 mg Ν L" . Bowman et al. (16) suggested that rapid biological immobilization, both by the turf and soil microorganisms, may reduce leaching losses from turf by limiting the period of time that the fertilizer Ν is resident in the soil.


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The objectives of this research were to determine the effects of salinity and Ν application rate on N 0 leaching and Ν mass emission from, and Ν uptake by tall fescue turf under greenhouse conditions. 3


MATERIALS AND METHODS Plant Culture. Research was conducted in a greenhouse maintained at 28/18°C day/night. Experimental conditions were chosen to maximize the potential for leaching, i.e. a porous sandy soil, fertilization with N H N 0 at relatively high rates, and irrigation considerably in excess of plant demand. Lysimeters were constructed from polyvinyl chloride (PVC) columns 15 cm in diameter and 60 cm deep. Each column was equipped with a porous ceramic cup (2.2 cm diameter by 7 cm long) which was embedded in 3 cm of diatomaceous earth layered at the bottom of the columns. The ceramic cup was connected via tubing to a 2 L collection bottle, which in turn was connected to a manifold vacuum line and pump equipped with a pressure gauge. Each column was packed with a sand (Table I) to a bulk density of 1.52 g cm" . Columns were seeded with "Monarch' tall fescue (Festuca arundinacea Schreb.) at a rate of 400 kg ha" . A fertilizer solution was applied at seeding to supply the equivalent of 50, 80 and 100 kg ha" Ν, Ρ and K , respectively. The turf was established for six months, during which time it was mowed every 7-12 days and irrigated twice each week. Ammonium nitrate was applied monthly at 50 kg Ν ha" during establishment. 4

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Table I. Particle size distribution of the sand used in the columns. Size Class

Percent of total

Sand Very Coarse (1-2 mm) Coarse (0.5-1 mm) Medium (0.25-0.5 mm) Fine (0.1-0.25 mm) Very Fine (0.05-0.1 mm) Silt/Clay

1.2 6.4 42.4 28.5 14.4 7.1

Treatments. Salt treatments were initiated January 13 and continued until final harvest of the columns on December 18. Treatment solutions were formulated to salt levels of 0,15 and 30 meq L" using tap water (EC 0.1 dS m ) and NaCl:CaCl in an 8:1 molar ratio. Each column was irrigated once with 1000 ml of the appropriate salt solution to rapidly equilibrate the columns. Thereafter the columns were irrigated approximately twice per week with a volume of solution calculated to maintain a 1

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3 0 % leaching fraction. The amount of irrigation was determined for each column by gravimetric mass balance. After each irrigation a vacuum of 0.010 MPa was applied to the ceramic cups for 1 6 hr to promote drainage. The collected leachate was weighed and subsampled for analysis. Nitrogen treatments were initiated February 12. Solutions of N H N 0 were prepared using the saline irrigation waters described above, and were applied to the columns monthly to supply 2 5 , 5 0 or 75 kg Ν ha" . Application volume was 3 0 0 ml column' , equivalent to a depth of 1.6 cm. To determine Ν allocation to new leaf growth, N H N 0 ( 9 . 9 8 % enrichment) was applied on September 11. Clippings collected during the subsequent month were pooled for N analysis. Additional Ρ and Κ were added at rates of 8 0 and 100 kg ha" , respectively on June 12. The experimental design was a two factor randomized complete block, with three salt levels, three nitrogen levels and four replicates. Significant differences were determined according to LSD (JP

Fate and Management of Turfgrass Chemicals - American Chemical

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