The relative effectiveness of broadcasting compared with band-placement of
phosphorus (P) fertilisers (0–480 kg P/ha) was compared using
potatoes grown on P-deficient sandy soils over 2 seasons in Western Australia
(Karrakatta sand in 1993, experiment 1; and Spearwood sand in 1996, experiment
2).
The maximum yield of potatoes when P fertiliser was broadcast and incorporated
to 20–25 cm before planting (broadcast) was 17 t/ha higher than when
P was placed in 2 bands 5 cm to the side of and below seed piece level
(banded) in experiment 1, and 13 t/ha higher in experiment 2. However,
higher rates of applied P were required to reach 99% of maximum yield
on the broadcast compared with the banded plots in both years (i.e. 174
v. 134 kg/ha in experiment 1, and 279
v. 125 kg/ha in experiment 2). Despite the lower
levels of applied P required to achieve maximum yield in the banding
treatment, banding P fertiliser for potatoes grown on Karrakatta and Spearwood
sands would result in significant economic loss.
The higher yield in the broadcast treatment corresponded with significantly
(P<0.001) higher P concentrations (about 2-fold) in
petioles of youngest fully expanded leaves from 56 to 131 days after sowing.
When tubers were 10 mm long, the petiole P concentrations corresponding with
95 and 99% of maximum yield were 1.13 and 1.28%, respectively,
for the broadcast P treatments in experiment 1, and 0.95 and 1.11% in
experiment 2. The reduced yield in the banded treatments was assumed to be due
to P fertiliser toxicity in the soil and not P toxicity in the plant tissue.
Phosphorus uptake by tubers was significantly
(P<0.001) higher (about 2-fold) when P was broadcast
rather than banded, especially at high levels of applied P. Phosphorus
recovery efficiency by tubers (P uptake by tubers/P applied, both in
kg/ha) was higher when P was broadcast rather than banded, particularly at
high levels of applied P (e.g. at 480 kg applied P/ha, recovery efficiency
was 0.07 in the broadcast treatment compared with 0.03 in the banded
treatment).
These results show that, for growers to avoid significant economic loss,
broadcast applications of P fertilisers should continue to be recommended for
potatoes grown on the low P-fixing, sandy soils of the Swan Coastal Plain.
Nutrients Recovery From Aquaculture Wastewater Using Thermally Treated Gastropod Shells
