title: Nitrogen removal and nitrate leaching for forage systems receiving dairy effluent.
abstract: Florida dairies need year-round forage systems that prevent loss of N to ground water from waste effluent sprayfields. Our purpose was to quantify forage N removal and monitor nitrate N (NO3(-)-N) concentrations in soil water below the rooting zone for two forage systems during four 12-mo cycles (1996-2000). Soil in the sprayfield is an excessively drained Kershaw sand (thermic, uncoated Typic Quartzipsamment). Over four cycles, average loading rates of effluent N were 500, 690, and 910 kg ha(-1) per cycle. Nitrogen removed by the bermudagrass (Cynodon spp.)-rye (Secale cereale L.) system (BR) during the first three cycles was 465 kg ha(-1) per cycle for the low loading rate, 528 kg ha(-1) for the medium rate, and 585 kg ha(-1) for the high. For the corn (Zea mays L.)-forage sorghum [Sorghum bicolor (L.) Moench]-rye system (CSR), N removals were 320 kg ha(-1) per cycle for the low rate, 327 kg ha(-1) for the medium, and 378 kg ha(-1) for the high. The higher N removals for BR were attributed to higher N concentration in bermudagrass (18.1-24.2 g kg(-1)) than in corn and forage sorghum (10.3-14.7 g kg(-1)). Dry matter yield declined in the fourth cycle for bermudagrass but N removal continued to be higher for BR than CSR. The BR system was much more effective at preventing NO3(-)-N leaching. For CSR, NO3(-)-N levels in soil water (1.5 m below surface) increased steeply during the period between the harvest of one forage and canopy dosure of the next. Overall, the BR system was better than CSR at removing N from the soil and maintaining low NO3(-)-N concentrations below the rooting zone.
authors.affiliation: Agronomy Dep., Univ. of Florida, IFAS, Gainesville, FL 32611, USA. krw@mail.ifas.ufl.edu
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Woodard
authors.forename: Edwin C
authors.initials: EC
authors.lastname: French
authors.forename: Lewin A
authors.initials: LA
authors.lastname: Sweat
authors.forename: Donald A
authors.initials: DA
authors.lastname: Graetz
authors.forename: Lynn E
authors.initials: LE
authors.lastname: Sollenberger
authors.forename: Bisoondat
authors.initials: B
authors.lastname: Macoon
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Portier
authors.forename: Brett L
authors.initials: BL
authors.lastname: Wade
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Rymph
authors.forename: Gordon M
authors.initials: GM
authors.lastname: Prine
authors.forename: Harold H
authors.initials: HH
authors.lastname: Van Horn
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D001682:Biological Availability; D002417:Cattle; D003612:Dairying; D004784:Environmental Monitoring; D009566:Nitrates / Q000032:analysis*; D009584:Nitrogen / Q000302:isolation & purification*; D018517:Plant Roots; D006109:Poaceae; D012989:Soil Pollutants / Q000032:analysis* / Q000378:metabolism; D014873:Water Pollutants / Q000032:analysis* / Q000378:metabolism; D003313:Zea mays
chemical_list: D009566:Nitrates; D012989:Soil Pollutants; D014873:Water Pollutants; D009584:Nitrogen