Nitrogen removal and nitrate leaching for two perennial, sod-based forage systems receiving dairy effluent.
In northern Florida, year-round forage systems are used in dairy effluent sprayfields to reduce nitrate leaching. Our purpose was to quantify forage N removal and monitor nitrate N (NO3(-)-N) concentration below the rooting zone for two perennial, sod-based, triple-cropping systems over four 12-mo cycles (1996-2000). The soil is an excessively drained Kershaw sand (thermic, uncoated Typic Quartzip-samment). Effluent N rates were 500, 690, and 910 kg ha(-1) per cycle. Differences in N removal between a corn (Zea mays L.)-bermudagrass (Cynodon spp.)-rye (Secale cereale L.) system (CBR) and corn-perennial peanut (Arachis glabrata Benth.)-rye system (CPR) were primarily related to the performance of the perennial forages. Nitrogen removal of corn (125-170 kg ha(-1)) and rye (62-90 kg ha(-1)) was relatively stable between systems and among cycles. The greatest N removal was measured for CBR in the first cycle (408 kg ha(-1)), with the bermudagrass removing an average of 191 kg N ha(-1). In later cycles, N removal for bermudagrass declined because dry matter (DM) yield declined. Yield and N removal of perennial peanut increased over the four cycles. Nitrate N concentrations below the rooting zone were lower for CBR than CPR in the first two cycles, but differences were inconsistent in the latter two. The CBR system maintained low NO3(-)-N leaching in the first cycle when the bermudagrass was the most productive; however, it was not a sustainable system for long-term prevention of NO3(-)-N leaching due to declining bermudagrass yield in subsequent cycles. For CPR, effluent N rates > or = 500 kg ha(-1) yr(-1) have the potential to negatively affect ground water quality.
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
Rymph
Stuart J
SJ
Wade
Brett L
BL
Prine
Gordon M
GM
Van Horn
Harold H
HH
D001673:Biodegradation, Environmental; D031744:Cynodon / Q000737:chemistry / Q000254:growth & development; D003612:Dairying; D009566:Nitrates / Q000737:chemistry / Q000302:isolation & purification*; D009584:Nitrogen / Q000737:chemistry / Q000302:isolation & purification*; D018517:Plant Roots; D012434:Secale / Q000737:chemistry / Q000254:growth & development; D012989:Soil Pollutants / Q000302:isolation & purification*; D014873:Water Pollutants / Q000302:isolation & purification*; D003313:Zea mays / Q000737:chemistry / Q000254:growth & development
D009566:Nitrates; D012989:Soil Pollutants; D014873:Water Pollutants; D009584:Nitrogen