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Availability of P from 32 P‐labelled endogenous soil P and 33 P‐labelled fertilizer in an alkaline soil producing cotton in Australia
Author(s) -
Dorahy C. G.,
Blair G. J.,
Rochester I. J.,
Till A. R.
Publication year - 2007
Publication title -
soil use and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.709
H-Index - 81
eISSN - 1475-2743
pISSN - 0266-0032
DOI - 10.1111/j.1475-2743.2007.00083.x
Subject(s) - fertilizer , soil water , chemistry , agronomy , soil test , phosphorus , alkali soil , fractionation , environmental science , soil science , biology , organic chemistry
Yield responses of irrigated, field‐grown cotton to phosphorus fertilizer application in Australia have been variable. In an attempt to understand better this variability, the distribution of fertilizer P within soil P fractions was identified using 32 P and 33 P radioisotopes. The soil chosen, an alkaline, grey, cracking clay (Vertosol), was representative of those used for growing cotton in Australia. Chang and Jackson fractionation of soil P from samples collected within 1 h of application indicated that 49, 7 and 13% of the P fertilizer was present as 0.5 m NH 4 F, 0.1 m NaOH and 1 m H 2 SO 4 extractable P, respectively. Over 89% of the P fertilizer was recovered as Colwell extractable P in these samples, suggesting that the majority of these reaction products was in a highly plant‐available form. Fertilizer‐P remained in an available form within the band 51 days after application, and 68% of the applied fertilizer‐P was recovered as Colwell‐P (1071 mg kg −1 ). The Colwell‐P concentration in the band was 35 times that in the unfertilized soil. Thus, the variability in crop response to P fertilizer application in these soils is not a consequence of fertilizer‐P becoming unavailable to plants. These results confirm the suitability of the Colwell (1963) sodium bicarbonate extraction method for measuring available P in these soils.