The residual value of superphosphate on a red-brown earth in South Australia

Abstract

The residual value of superphosphate on a red-brown earth naturally deficient in phosphate has been determined by means of a field experiment. pot trials. and chemical extractions . In a field experiment on a site where 24½ cwt of superphosphate per acre had been previously applied over a period of 23 years, it was found that wheat. in a wheat-barley-fallow rotation. could be grown for 5 years before a clearly defined response developed to superphosphate currently applied at 11 lb (P1) or 22 lb (P2) phosphorus pentoxide (P2O5 ) per acre . Stubble-sown barley showed a response after the first year.

Increasing phosphorus supply in subsurface soil in northern Australia: Rationale for deep placement and the effects with various crops

“…Rapid drying of the soil surface is likely to have occurred at all 3 sites because of the high temperatures and associated evaporative demand (Tables 1 and 2). Drying of surface soil has been previously shown to restrict the uptake of surface-applied P for a number of crops (Piper and de Vries, 1964;Scott, 1973;Jarvis and Bolland, 1991). Other workers have shown how P uptake from the soil is directly related to the soil water content; extra soil water assists the diffusion of phosphate ions through the soil solution to the root surfaces (Nye and Tinker, 1977) by lowering the tortuosity of the diffusion path and increasing the cross-sectional area of the diffusion pathway (Mackay and Barber, 1985).…”

“…This will be the case for P as the diffusion of phosphate ions to plant roots is limited in dry soil (Nye and Tinker, 1977). Indeed the drying of surface soil has been shown to restrict the uptake of surface -applied P in wheat (Piper and de Vries, 1964), annual medic (Scott, 1973) and lupins (Jarvis and Bolland, 1991). One approach to this problem is to place P fertiliser deeper in the soil.…”

A review of phosphorus efficiency in wheat

“…The PE ratios reported for plants grown in the field under dryland conditions range from about 250-565 kg grain kg p-1 in shoots (Batten and Khan, 1987a;Piper and de Vries, 1964;Smith, 1965). Plants grown under controlled environmental conditions have PE ratios ranging from as low as 40 to as high as 715 g grain g p-1 in shoots (Batten, 1986a;Jessop et al, 1984;Lipsett, 1964).…”

The efficiency of utilisation of P in superphosphate

“…On the other hand, this initial rate of loss seems not to be maintained, and so it is quite consistent that repeated applications will build up a reserve of phosphate. If phosphate is then withheld, responses to phosphate may not be obtained -as has been observed (Piper & de Vries 1964).…”