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Decrease in phosphorus concentrations when P fertiliser application is reduced or omitted from grazed pasture soils


Coad, J and Burkitt, L and Dougherty, W and Sparrow, L, Decrease in phosphorus concentrations when P fertiliser application is reduced or omitted from grazed pasture soils, Soil Research, 52, (3) pp. 282-292. ISSN 1838-675X (2014) [Refereed Article]

Copyright Statement

Journal compilation copyright 2014 CSIRO

DOI: doi:10.1071/SR13243


Many intensively managed soils contain phosphorus (P) concentrations greater than required for optimum production. Soils with P concentrations in excess of the agronomic optimum can have unnecessary losses of P that can adversely affect water bodies. Reducing excessive soil-P concentrations is important for the economic and environmental sustainability of intensive agriculture, such as the Australian dairy industry. However, little is known of decreases in extractable soil-P concentrations when P fertiliser applications are reduced or omitted from soils with P concentrations and properties representative of intensive pasture grazing systems. Decreases in extractable P (calcium chloride (CaCl2), Olsen and Colwell) were monitored for up to 4.5 years for six Australian grazed pasture soils (Red Ferrosol, Brown Kurosol, Grey Dermosol, Brown Dermosol, Podosol and Hydrosol) with contrasting textures and P-buffering indices (PBI). Sixteen treatments consisting of four initial extractable-P concentrations (Pinit) paired with four ongoing P fertiliser rates (Pfert) were established for each of the six soils, except on an extremely low-PBI Podosol, where a range of Pinit concentrations could not be established. The resultant decreases in P were larger with higher Pinit concentration and lower rate of ongoing Pfert, except in the extremely low PBI Podosol where decreases in initially high CaCl2-P concentrations were large irrespective of ongoing Pfert. There was a greater proportional decrease in the environmentally extractable P compared with agronomically extractable P, with mean decreases in CaCl2-P of 57%, Olsen-P of 25%, and Colwell-P of 12%. The Pinit concentrations, which were well above agronomic optimum, remained above this target. This study advances scientific knowledge of extractable soil-P concentrations when P fertiliser inputs are withheld or reduced from grazed pasture soils, and aids land and catchment managers in estimating likely changes over time.

Item Details

Item Type:Refereed Article
Keywords:soil, phosphorus, Olsen P, decline with time, utilise, withdrawal
Research Division:Environmental Sciences
Research Group:Soil sciences
Research Field:Soil sciences not elsewhere classified
Objective Division:Plant Production and Plant Primary Products
Objective Group:Other plant production and plant primary products
Objective Field:Other plant production and plant primary products not elsewhere classified
UTAS Author:Coad, J (Ms Coad)
UTAS Author:Sparrow, L (Dr Leigh Sparrow)
ID Code:93100
Year Published:2014
Web of Science® Times Cited:8
Deposited By:Tasmanian Institute of Agriculture
Deposited On:2014-07-11
Last Modified:2017-10-31

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