New Zealand Journal of Agricultural Research abstracts
Effect of sheep stocking intensity on soil physical properties and dry matter
production on a Pallic Soil in Southland
J. J. DREWRY
AgResearch
C/- Department of Soil and Physical Sciences
P.O. Box 84
Lincoln University
Canterbury, New Zealand
J. A. H. LOWE
Otago Regional Council
Private Bag
Dunedin, New Zealand
R. J. PATON
AgResearch
Invermay Agricultural Centre
Private Bag 50034
Mosgiel, New Zealand
Abstract This 3-year study examined the extent of damage to
soil physical properties of a Pukemutu silt loam (Pallic Soil) and the loss of
ryegrass-white clover pasture production caused by intensive winter grazing at
1800 sheep ha-1. Macroporosity, pore size distribution, bulk
density, and hydraulic conductivity were measured at 5-cm incremental soil
depths to 15 cm to assess changes in soil compaction. Soil smearing on
intensively winter-grazed plots suggested that soil structural damage had
occurred. Soil physical tests, three weeks after winter grazing, in August 1994
and 1995, however, showed only slight compaction at the surface. Macroporosity
in the 0-5 cm soil depth was significantly reduced from 16.4% to 12.1% by the
intensive winter grazing treatment. Soil pores were water-filled leading to
plastic deformation rather than compaction. Spring pasture production was also
significantly decreased (21%) following the 1994 winter grazing, but growth
recovered the following summer. Macroporosity was generally greater than 10% so
was unlikely to limit production for long at this site.
Keywords compaction; Southland; sheep; treading; soil
physical properties; macroporosity
New Zealand Journal of Agricultural Research, 1999, Vol. 42: 493-499
0028-8233/99/4204-0493 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (555K); (scanned from paper original: notes about this process)
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