Phosphorus Use-Efficiency by Cotton Grown in an Alkaline Soil as Determined Using ³²Phosphorus and ³³Phosphorus Radio-Isotopes

ABSTRACT

³²Phosphorus (P) and ³³P radioisotopes were used to identify the contribution of soil and fertilizer P sources to P uptake by cotton (Gossypium hirsutum L.) grown in an alkaline soil representative of those used for growing cotton in Australia. Phosphorus fertilizer application only increased P concentration in the plants during leaf expansion, but had no effect on biomass production, P uptake at later growth stages sampled, or lint yield. However, at flowering, more than 50% of the P taken up was derived from within the fertilized band of soil, even though recovery of the 45 kg P ha⁻¹ applied was low (1.2–3.4%). Phosphorus fertilizer application did not increase lint yield of cotton in this soil. Although P fertilizer recovery was poor, P fertilizer remained in an available form throughout the experiment indicating that pre-plant applications can remain effective. However, they will only be beneficial when soil P is limiting to crop growth.

Keywords:

• P availability
• P use-efficiency
• Vertosol
• nutrition
• recovery

ACKNOWLEDGMENTS

This work was funded by the Australian Cotton Cooperative Research Centre (Project 5.3.1). Dr Nelly Blair, Kate Dorahy, Judi Kenny, Leanne Lisle, Greg Roberts and Dr Anthony Whitbread provided valuable technical assistance.

Notes

∗ = P < 0.05;—= not determined.

^ALint yield (g container⁻¹).