Nitrogen uptake and nitrate (NO-3)
leaching below 1.1 m was estimated under phalaris, cocksfoot, and annual
ryegrass pastures and under bare fallow in a 4-year field experiment under
control and high N (500 kg N/ha) treatments in north-eastern Victoria (693
mm/year rainfall for the study period). The perennial grasses,
particularly phalaris, took up more N in herbage than annual ryegrass. High
concentrations of NO3-N were measured at 1 m depth
below all treatments, suggesting that NO3- losses from
pastures have potential to contaminate streams and/or groundwater.
Perennial pastures were only able to reduce NO3-
leaching compared with annuals in drier than average years. Values calculated
for acid addition due to NO3-leaching resulted in a net
annual input of approximately 1 kmol H +/ha.year
under the phalaris pasture compared with 2 kmol H
+/ha.year under annual ryegrass. Adding these
figures to carbon cycle addition data of 1 kmol
H+/ha.year (measured in a previous study)
corresponds to a lime rate of 100 and 150 kg lime/ha.year being required
to stop further acidification under these pasture types. A 1 unit pH decline
to 30 cm depth was estimated to take 42 years under annual pasture or 67 years
under perennial grasses. Whilst perennial pastures have a role in reducing
soil acidification, lime application is the most important management option
in balancing soil acidification caused by agriculture.
Sulfur fertilization strategy affects grass yield, nitrogen uptake, and nitrate leaching: A field lysimeter study
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