Factors affecting the change in extractable phosphorus following the application of phosphatic fertiliser on pasture soils in southern Victoria
journal contributionposted on 2023-05-16, 14:06 authored by Burkitt, LL, Gourley, CJP, Sale, PWG, Uren, NC, Hannah, MC
Nine pasture soils from high rainfall zones of southern Victoria were analysed for a range of chemical and physical properties before receiving a single application of P fertiliser in the form of triple superphosphate (TSP), single superphosphate (SSP), or TSP and lime (5 t/ha) at amounts ranging from 0 to 280 kg P/ha. Soils were analysed for bicarbonate-extractable P concentration, using both the Olsen P and Colwell P methods, 6 and 12 months after fertiliser application. A strong positive linear relationship existed at all sites between the amount of P applied and both the Olsen P and Colwell P concentrations. The slopes of these relationships measured the change in extractable P concentration (Î”EP) per unit of P applied, whilst the inverse of the Î”EP value indicated the amount of P fertiliser required above maintenance to increase the extractable P concentration by 1 mg/kg. These values ranged from 5 to 15 kg P/ha, depending on soil type. The Î”EP measured by the Olsen (Î”EPOlsen) method was closely related to selected soil properties and P sorption measures, whilst the Î”EPColwell values were also closely related to selected soil properties and P sorption measures, but only when one particular site, an acidic sand, with a high organic carbon content was excluded from the analysis. In general, simple, direct measures of soil P sorption could allow the estimation of Î”EP values on different soil types. The application of P in the form of SSP resulted in a trend for higher Î”EP values than occurred with TSP. This difference was significant on 3 sites (P < 0.05), but depended on the method of extraction and the time after fertiliser application. The application of lime significantly (P < 0.001) increased soil pH (H2O and CaCl2) and decreased the concentration of exchangeable Al, 6 months after treatments were applied, but generally had little impact on Î”EP values.
Publication titleAustralian Journal of Soil Research
Department/SchoolTasmanian Institute of Agriculture (TIA)
Place of publicationMelbourne, Australia