Changes in pasture and soil properties with liming and superphosphate application over 12 years, on five soils in the Central Tablelands of New South Wales

Peter Dowling; Ian Vimpany; Mark Conyers; Geoffrey Millar; Keith Helyar; David Michalk; Helen Nicol; Jim Bradley; Paul Milham; Richard Hayes

Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Changes in pasture and soil properties with liming and superphosphate application over 12 years, on five soils in the Central Tablelands of New South Wales

Peter Dowling, Ian Vimpany, Mark Conyers , Geoffrey Millar, Keith Helyar, David Michalk, Helen Nicol, Jim Bradley, Paul Milham, Richard Hayes

Abstract

Context. The decision to lime pastures requires understanding of the benefits and their duration. Aims. The enduring effects of contrasting rates of superphosphate and lime on soil chemistry and pasture productivity were quantified on 5 acidic soils over 12 y. Methods. The sites were established in 1978 on the Central Tablelands of New South Wales, Australia. Initial treatments of lime were 0, 0.63, 1.25, 2.5 and 5.0 t/ha. Single superphosphate (SSP) was top-dressed annually at 0, 125 and 250 kg/ha. Key results. Averaged across the 5 sites, the initial pH increase due to liming was 0.3 units/t, and 12 y later had declined to 0.1 pH units/t. In the absence of lime, soil pH declined by ~0.02 units/y, and across all lime treatments and sites, the annual decline averaged ~0.07 units/y. Annual applications of SSP were associated with lower soil pH and exchangeable soil potassium (K), and higher Al saturation, but differences required 2 - 7 y to emerge. There was an almost universal increase in annual dry matter associated with SSP application, which often reduced the percentage of weeds. Lime generally increased pasture biomass, with pastures dominated by T. subterraneum more responsive than those dominated by D. glomerata. Pasture yields generally increased with exchangeable Ca but yield responses to %Al were more variable. Implications. The historical view of lime and SSP being alternative investments is counterproductive. Pasture renovation may be necessary to realise the full benefit of lime and SSP application.

CP24336 Accepted 17 April 2025