Effect of plant populations and row spacings on early and late maize hybrids in the Ord Valley

Abstract

The effect of three row spacings (50 cm, 75 cm and 100 cm) and three plant populations (44,500, 59,300 and 89,000 plants ha-1) on two maize cultivars (short, early XL 45 and tall, late Q 692) was investigated at Kimberley Research Station. None of the crop measurements was significantly affected by row spacing. Tasselling, silking and maturity occurred respectively 10, 12 and 16 days later in Q 692 than in XL 45. Their time of occurrence was not affected by populations. Q 692 was considerably taller and had more leaves per plant. Its canopy thickness above the cobs was also considerably greater. At silking, total dry matter was higher in Q 692, and in both cultivars higher at higher population densities. The production of dry matter after silking increased with increasing populations in XL 45 but declined in Q 692. The grain yield of XL 45 increased significantly up to 59,300 plants ha-1 and then levelled off. On the other hand the yield of Q 692 fell significantly with each population increase. Population had no effect on mean seed weight, which was slightly higher in Q 692. The detrimental effects of increasing population on the number of barren plants and on the number of seeds per cob were offset by the higher number of cobs per hectare in XL 45 but not in Q 692. Nitrogen and phosphorus contents were not affected by populations and were similar in both hybrids