Phosphorus and nitrogen fertiliser effects on anion-exchange-resin phosphorus and sugarcane yield in Plinthic soils of KwaZulu-Natal, South Africa

Abstract

Efficient phosphorus (P) extraction methods are vital for optimising sugarcane production, yet no single chemical extractant currently suits the diverse soil conditions across South Africa’s sugarcane regions. This study explored the potential of anion-exchange-resin phosphorus (AER-P) as a possible alternative to conventional P extractants. The novelty of this study lies in evaluating AER-P in the local context, offering a potential unified method for P assessment across varying soils. The field experiment involved varying levels of P and nitrogen (N) applied in a randomised design with four replications. The results revealed that soil AER-P increased significantly (p < 0.05) with increase in P fertiliser from 8.52 to 49.91 mg l^{− 1} and positively correlated with P concentration in sugarcane leaves. Leaf P and yield properties tracked AER-P at moderate strength (R² ≈ 0.50–0.52) and plateaued at ∼40 mg l^{− 1} of AER-P associated with the rate of 100 kg P ha^{− 1}. Elevated N levels led to a notable decrease in soil pH and a modest decline in base cations and cation exchange capacity (CEC). These findings highlight the potential of AER-P as a reliable indicator of P availability in sugarcane soils. However, a broader validation across multiple seasons and climatic zones is necessary before widescale adoption.