Author:
Silva R. G.,Cameron K. C.,Di H. J.,Smith N. P.,Buchan G. D.
Abstract
A field lysimeter experiment was conducted to determine the effect of
macropore flow on the transport of surface-applied cow urine N through soil.
The lysimeters (500 mm diameter by 700 mm depth) used for this experiment were
collected from Templeton fine sandy loam soil (Udic Ustochrept), which had
been under ryegrass (Lolium perenne L.) and white clover
(Trifolium repens L.) pasture for 9–10 years. The
effect of macropore flow on urine-N leaching was determined by leaching
experiments under 0.5 kPa and 0 kPa water tensions (suctions) imposed on top
of the lysimeter using a disc tension infiltrometer. The 0.5 kPa suction
prevented soil pores >600 µm diameter from conducting water and
solutes, while the 0 kPa suction allowed conduction under ‘field
saturated’ condition. Pores >600 µm diameter transmitted about
98% of the total nitrogen (N) leached below 700 mm depth. The main form
of N transmitted under 0 kPa was ammonium (NH4 -N),
accounting for 10.5% of the total N applied at 0 kPa suction. This was
significantly higher than the amount of NH 4 -N leached at 0.5 kPa suction,
which accounted for 0.17% of N applied. The urea-N in the leachate
reached 16 mg/L at 0 kPa suction, and accounted for 1.6% of the
total N applied. No urea was detected in the leachate at the 0.5 kPa suction.
The concentrations and amounts of nitrate (NO3 -N)
leached were very low and did not differ between the two suctions. The forms
and amounts of N leached were affected by the interactions of macropore flow
and N transformations in the soil, and the environmental conditions during the
two leaching events. From this work, it is recommended that stock should be
removed 1–2 days before irrigation water is applied as this will allow
animal urine to diffuse into soil micropores and thus decrease N leaching by
macropore flow.
Subject
Earth-Surface Processes,Soil Science,Environmental Science (miscellaneous)
Cited by
27 articles.
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