Nutrient requirements for irrigated lucerne in Central Otago

Abstract Two field trials were commenced in September 2000 on newly sown irrigated lucerne near Tarras in Central Otago. The first trial measured the effects of phosphorus (P) (0, 30, 60, 120 kg P/ha) and potassium (K) (0, 50, 100, 200 kg K/ha) fertiliser applications while the second trial determined nitrogen (N) requirements for lucerne establishment. Initial soil test levels (0-75 mm) were pH 5.6, Olsen P 15 I¼g/ml; quicktest (QT) K 6 and sodium tetra-phenol-boron extractable K (TBK) 3.1. Lucerne production averaged 9.5 t dry matter (DM)/ha in the establishment year, 15.6 t DM/ ha in Year 2 and 14.8 t DM/ha in Year 3. There were no annual DM responses to any of the three fertilisers applied regardless of the rate of application. Despite the control mean annual herbage P concentrations being within the optimum range of 0.20-0.25% the application of P fertiliser significantly increased the P concentrations (P