Phosphorus application rate, and time after application, affect soil and leaf phosphorus concentrations in an upland Western Cape apple orchard

Abstract

The effects of different rates of phosphorus (P) applied during soil preparation on leaf and soil P concentrations, and on leaf K, were investigated in a field trial in which Starking apple trees were grown on a limed, initially low-P (<1.5 mg kg⁻¹) Pinedene soil on Bokkeveld shale in the Vyeboom area, South Africa. Single superphosphate (10.5% P) was applied at rates of 0, 590, 1210 and 2370 kg ha⁻¹ during soil preparation. These promoted Bray II soil P concentrations of 1.4, 7.5, 10.3 and 29.6 mg kg⁻¹, respectively, in season one. Soil P concentrations decreased with time thereafter, supporting adequate leaf P concentrations for time intervals that increased with initial P application rate, but which, even at the maximum P application rate, did not exceed six seasons. Leaf K bore no significant relationship to soil or leaf P concentrations.