Loretta Serafin1, Mark Hellyer1 and Neroli Graham1
Four field experiments were conducted in the 2014-15 and 2015-16 seasons to compare interactions among nitrogen rates, application timing and maize hybrids. Two experiments were conducted at Gurley, south of Moree, under rain-fed conditions and two were conducted at Breeza, on the Liverpool Plains, under irrigated conditions. Nine nitrogen treatments were imposed in each experiment with seven treatment rates, ranging from 0 to 250 kg N/ha applied upfront at sowing, and two split treatments of 75:75 and 100:100 kg N/ha with half applied at sowing and half at the 6-8 leaf growth stage. Two medium maturity maize hybrids, Pac606 and Pioneer 1467 were selected for comparison. Biomass production was highest from the 100 kg N/ha and 75:75 split treatments in both hybrids, and the 150 kg N/ha treatment in Pac606. The lowest plant biomass was obtained from the 250 kg N/ha and 100:100 split treatment in both hybrids.
A positive linear yield response to N application was seen in both Pac606 and Pioneer 1467 with the highest yield obtained with the application of 250 kg N/ha. The 100:100 split application treatment reduced plant biomass when compared to 200 kg N/ha applied upfront but achieved similar yields. Kernel number had a strong correlation with grain yield but there was either no correlation or a weak association between plant biomass and grain yield with each of the hybrids. These results suggest splitting N application with 100 kg N/ha applied at sowing and 100 kg N/ha applied at the 6-8 leaf growth stage could be an appropriate strategy to maximise water use efficiency of maize under both rain-fed and irrigated production systems in northern NSW.