Loretta Serafin1, Mark Hellyer1, Andrew Bishop1 and Annie Warren1
Tillering in grain sorghum can be either an advantage or a disadvantage, depending on the growing environment and the plant population. The challenge is to match the genetics and management to the site and expected environmental conditions. Commercial hybrids are marketed with information on the level of tillering likely to be expressed.
Three experiments were conducted in 2017-18 at Gurley, Mallawa and Breeza, in Northern NSW under rain-fed conditions, to compare the impact of plant density on tillering in four grain sorghum hybrids.
Hybrids were selected based on their levels of tillering from low to high. The industry standard MR Buster was compared to Agitator, Brazen and Archer.
At Gurley and Breeza, four plant densities, 30, 60, 90 and 120,000 plants/ha were targeted. At Mallawa the 120,000 treatment was replaced with 45,000 plants/ha. The row spacing was 100cm at Breeza and Gurley and 150cm at Mallawa.
Total tiller number showed a negative correlation with increasing plant density. Differences in tillering were detected between hybrids, but their tiller level was not consistent with expectations. Archer produced the lowest number of tillers in all three experiments, and Agitator the highest. Differences (in tillering) between the hybrids were also smaller than anticipated. The difference in tillering was greatest at the lowest plant densities (1.5 tillers per plant, between hybrids) and these differences became smaller as plant density increased. There was no impact of plant density on yield at Gurley and Mallawa, or on harvest index across all sites. At Breeza; the mildest growing environment; Archer produced the highest grain yield.