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Nitrate leaching loss under annual and perennial pastures with and without lime on a duplex (texture contrast) soil in humid southeastern Australia
Author(s) -
Ridley A. M.,
White R. E.,
Helyar K. R.,
Morrison G. R.,
Heng L. K.,
Fisher R.
Publication year - 2001
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1046/j.1365-2389.2001.00387.x
Subject(s) - leaching (pedology) , agronomy , surface runoff , perennial plant , lime , lessivage , nitrate , trifolium repens , lolium perenne , loam , environmental science , soil water , chemistry , geology , soil science , biology , ecology , paleontology , organic chemistry
Summary 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 CaCl 2 ) 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 NO 3 – 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 NO 3 – comprising 70–77%. No NO 3 – 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 NO 3 – 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 NO 3 – 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.