ISSN:
1365-2389
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Mineral N accumulates in autumn under pastures in southeastern Australia and is at risk of leaching as nitrate during winter. Nitrate leaching loss and soil mineral N concentrations were measured under pastures grazed by sheep on a duplex (texture contrast) soil in southern New South Wales from 1994 to 1996. Legume (Trifolium subterraneum)-based pastures contained either annual grass (Lolium rigidum) or perennial grasses (Phalaris aquatica and Dactylis glomerata), and had a control (soil pH 4.1 in 0.01 m CaCl2) or lime treatment (pH 5.5). One of the four replicates was monitored for surface runoff and subsurface flow (the top of the B horizon), and solution NO3– concentrations.The soil contained more mineral N in autumn (64–133 kg N ha−1 to 120 cm) than in spring (51–96 kg N ha−1), with NO3– comprising 70–77%. No NO3– leached in 1994 (475 mm rainfall). In 1995 (697 mm rainfall) and 1996 (666 mm rainfall), the solution at 20 cm depth and subsurface flow contained 20–50 mg N l−1 as NO3– initially but 〈 1 mg N l−1 by spring. Nitrate-N concentrations at 120 cm ranged between 2 and 22 mg N l−1 during winter. Losses of NO3– were small in surface runoff (0–2 kg N ha−1 year−1). In 1995, 9–19 kg N ha−1 was lost in subsurface flow. Deep drainage losses were 3–12 kg N ha−1 in 1995 and 4–10 kg N ha−1 in 1996, with the most loss occurring under limed annual pasture. Averaged over 3 years, N losses were 9 and 15 kg N ha−1 year−1 under control and limed annual pastures, respectively, and 6 and 8 kg N ha−1 year−1 under control and limed perennial pastures. Nitrate losses in the wet year of 1995 were 22, 33, 13 and 19 kg N ha−1 under the four respective pastures. The increased loss of N caused by liming was of a similar amount to the decreased N loss by maintaining perennial pasture as distinct from an annual pasture.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1365-2389.2001.00387.x
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