Agronomic response of sorghum to nitrogen management – Tamworth 2014–15

Abstract

Key findings • Despite only 71 mm (0–150 cm) of plant available water (PAW) at sowing, in-crop rainfall of 392 mm substantially increased yield potential. • There was a significant grain yield response to applied nitrogen (N). Adding 40 kg N/ha resulted in a 0.9 t/ha or 10% increase in grain yield over the nil applied N treatment. • Optimum yield was achieved through applying 160 kg N/ha, which resulted in a 21% or 1.7 t/ha increase in grain yield over the nil treatment. There was a corresponding 10% increase in yield with the 40 kg N/ha treatment. • Maximum grain yields were achieved when grain protein was >9.0%, supporting previous observations that the critical grain protein value of sorghum is 9–10% to maximise yield. • These results highlight the need to consider yield potential in terms of probable and starting soil N values.