Effects of seeding rate and fertiliser on crop development and seed production of ‘Grasslands Tama’ Westerwolds ryegrass

Abstract

‘Grasslands Tama’ Westerwolds ryegrass seed crops were sown at 3 seeding rates (15, 30, and 60 kg seed/ha) on a soil of moderately low fertility at Kirwee in Central Canterbury. At each rate 2 crops were grown, 1 with NPK fertiliser applied at sowing, the other with fertiliser applied after floral initiation, treatments designed to stimulate vegetative or reproductive growth, respectively. Tiller numbers per unit area declined as crops progressed from vegetative to reproductive growth, but seeding rate or fertiliser treatments had no effects except in November 1974 when crops sown at 60 kg/ha had more tillers per unit area than the other crops. Up to September 1974, and only for crops sown with fertiliser, individual tiller weights decreased with increased seeding rate. There was no seeding rate effect on tiller weights for crops sown with fertiliser, these tillers being generally lighter than those in crops sown with fertiliser. In November 1974, some 7 weeks after floral initiation fertiliser had been applied, tiller weights decreased with increased seeding rate, but the fertiliser treatment effect was no longer apparent except at the 60 kg/ha seeding rate. Except for the 60 kg/ha rate, crops sown with fertiliser had a higher proportion of large seed heads (> 28 spikelets per spike) than crops with fertiliser after floral initiation. Crops at the lightest rate had heaviest individual seeds, but seeding rate had no significant effects on seed yield; crops sown with fertiliser yielded less than crops with fertiliser after floral initiation (790 and 1000 kg/ha respectively).