Effect of seeding systems and dinitroaniline herbicides on emergence and control of rigid ryegrass (Lolium rigidum) in wheat

Experiments were conducted at Minlaton on the Yorke Peninsula of South Australia in 2004 and 2005 to study the effect of four different seeding systems and dinitroaniline herbicides on the seedling emergence and growth of rigid ryegrass in wheat. The seeding systems were low soil-disturbance discs (DayBreak and K-Hart) and high soil-disturbance tines (narrow point and Ribbon seeder); and the herbicides were oryzalin, pendimethalin, and trifluralin at rate of 0.72 kg ai/ha. The total seedling emergence of rigid ryegrass was higher in nontreated plots planted with the tines compared with the discs. In general, oryzalin was the least-effective herbicide in controlling emergence of rigid ryegrass. All herbicides were more effective in reducing the number of plants, spikes, dry matter, and seed production of rigid ryegrass in combination with tines than with discs. However, in the absence of herbicides, plant and spike numbers, plant dry weight, and seed production of rigid ryegrass were significantly lower where discs were used to sow, rather than tines. In the absence of herbicide, rigid ryegrass was less competitive with wheat under the disc-sown systems. The response of grain yield to herbicides was greater under the tine-sown systems than the disc-sown systems.