Nitrogen removal and nitrate leaching for forage systems receiving dairy effluent.
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.
Woodard
Kenneth R
KR
Agronomy Dep., Univ. of Florida, IFAS, Gainesville, FL 32611, USA. krw@mail.ifas.ufl.edu
French
Edwin C
EC
Sweat
Lewin A
LA
Graetz
Donald A
DA
Sollenberger
Lynn E
LE
Macoon
Bisoondat
B
Portier
Kenneth M
KM
Wade
Brett L
BL
Rymph
Stuart J
SJ
Prine
Gordon M
GM
Van Horn
Harold H
HH
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
D009566:Nitrates; D012989:Soil Pollutants; D014873:Water Pollutants; D009584:Nitrogen