
TY  - JOUR
A1  - Strong, W. M. 
A1  - Best, E. K. 
A1  - Cooper, J. E. 
T1  - Phosphate fertiliser residues in wheat-growing soils of the Western Downs, Queensland
JF  - Soil Research
JO  - Soil Res.
Y1  - 1997
VL  - 35
IS  - 2
SP  - 341
EP  - 354
KW  - P soil test, P uptake, Vertisol, sodic subsoil, predicting soil test.
UR  - https://doi.org/10.1071/S96038 
N2  - Effects of repeated annual application and residual effects of past phosphorus (P) applications were studied at Billa Billa and The Gums, Queensland, on 2 Vertisols representative of a large cropping area in this region. Phosphorus was applied annually at 0, 4, 8, 12, and 25 kg/ha at sowing to each wheat crop between 1978 and 1988. Phosphorus was also applied at 25, 50, 100, 200, or 400 kg/ha as a once-only application, before wheat was sown in 1978, and was incorporated by tillage. Pot experiments were conducted each year with soil (6 kg/pot) gathered from field plots in May before wheat sowing to determine the residual value (RV) of previously applied P fertiliser under standard conditions of frequent watering. In 1979 the RV was determined in a second series of pots with a water deficit to simulate conditions of plant moisture stress that were to dominate the field experiments. The RV of P fertiliser was reduced to one-third that determined under well-watered conditions. Low residual values (8&#8211;47%) determined in the field in 1979 for P rates 25 and 50 kg/ha applied in 1978 were probably due to reduced P uptake from dry topsoil throughout which P residues were incorporated by tillage. By contrast, P applied annually at a low rate (4 or 8 kg/ha) in a band close to seeds created profitable responses when evaluated over the sequence of successive wheat crops. The bicarbonate-extractable soil test value (Pbf) on either soil fertilised annually for n years with P at a rate R (kg/ha&#183; year) was described by the model where Pbu is the soil test value (mg/kg) of unfertilised soil. 
ER  -

