Changes in forms of soil inorganic phosphorus in Lismore stony silt loam due to application of superphosphate to pasture

Abstract

Changes in available phosphorus (as extracted by the Truog and Olsen methods) and in phosphorus held in the soil in aluminium-, iron-, and calcium-bound forms have been followed on soil samples taken from a rates of superphosphate trial on irrigated pasture from 1952 to 1964.Truog phosphorus levels in samples taken at three-monthly intervals showed a cyclic pattern due to the annual fertiliser applications, the fluctuations being greater at higher rates of superphosphate.In samples taken just before top-dressing each autumn, 3 cwt and 4t cwt of superphosphate applied annually caused a net increase in levels of aluminium-, iron-, and calcium-bound phosphorus, the aluminium-bound form increasing more than the other two forms. However. this form was also depleted at a greater rate than iron-or calcium-bound phosphorus during the residual phase of the trial. On these samples, the Truog and Olsen methods gave a pattern of phosphorus accumulation and depletion closely correlated with the aluminium-bound form, which is considered to be the most important source of phosphorus for plant uptake on this soil type.

Effect of superphosphate applications on soil phosphorus and on crop phosphorus removal by the strawberry

“…Similar to the findings of Grigg 11 Evidently, as fixation became more complete in the "FePOj," The lack of a significant yield response to superphosphate lu additions indicated that the relatively low soil P levels in the control plots were adequate for the strawberry cv.…”

Effect of long-term irrigation on stony soils of the Canterhury Plains

“…Mean ir.organic phosphorus concentrations in the 1971 samples from irrigated and control sites were slightly less than the mean concentrations of the 1945 samples. Grigg (1966) reported a decrease with time in the aluminium-bound phosphorus content of irrigated Lismore stony silt loam at a fertiliser rate of 190 kg superphosphate/ha/yr, but not at higher rates of superphosphate application. As the mean superphosphate application on the sites being discussed was 190 kg/yr, it is suggested that the decreases in inorganic phosphorus found in the 1971 samples could reflect the same effect as that reported by Grigg.…”