Abstract
The leaching of nitrate
(NO3–) in intensive
agricultural production systems, e.g. dairy pastures, is a major environmental
concern in many countries. In this lysimeter study we determined the amount of
NO3– leached following the
application of urea, dairy effluent, urine returns, and pasture renovation to
a freedraining Lismore stony silt loam (Udic Haplustept loamy skeletal)
growing a mixture of perennial ryegrass (Lolium perenne)
and white clover (Trifolium repens) pasture. The study
showed that NO3–-N leaching
losses ranged from 112 to 162 kg N/ha per year, depending on the amount
and forms of N applied and pasture conditions. Nitrate leaching under the
urine patches was the main contributor to the N leaching loss in a grazed
paddock. Nitrate leaching losses were lower for urine applied in the spring
(29% of N applied) than for urine applied in the autumn
(38–58%). The application of urea or dairy effluent only
contributed a small proportion to the total
NO3– leaching loss in a
grazed paddock. Pasture renovation by direct-drilling may also have caused an
increase in NO3– leaching
(c. 31 kg N/ha) in the first year. Modelled annual average
NO3–-N concentrations in the
mixed recharge water in the acquifer were significantly lower than those
measured under the rooting zone due to dilution effects by recharge water from
other sources (3.9 v. 13–27 mg N/L). Herbage
nitrogen offtake and dry matter yield were higher in the urine treatments than
in the non-urine treatments.
groundwater, denitrification, mineralisation, grazing, forage.
Subject
Earth-Surface Processes,Soil Science,Environmental Science (miscellaneous)
Cited by
91 articles.
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