Accelerating giant rat’s tail grass (GRT) soil seed bank depletion through chemigation

Abstract

The successful management of the giant rat’s tail grass (GRT) is dependent on depleting the large soil seed bank reserves, preventing emerging seedlings from reaching reproductive maturity and controlling established tussocks. Though an array of integrated control options is available, control is often met with varying degrees of success due to the ten years of soil seed bank longevity. A laboratory experiment was conducted at the Ecosciences Precinct in Brisbane to investigate the efficacy of dazomet in accelerating the depletion of the GRT soil seed bank. To determine the effectiveness of dazomet, 25 glass jars were filled with a sandy loam soil to which GRT seed sachets containing 100 seeds were buried to a depth of 2 cm. Dazomet treatments consisted of 0 (control), 41.25, 82.5, 165 and 330 kg a.i. ha-1 were replicated five times. Following 30 days of fumigation exposure, the seeds were retrieved and tested for viability using 1% 2,3,5triphenyltetrazolium chloride (TTC). Regardless of application rate, dazomet was effective and significantly reduced the viability rate of GRT seeds when compared to the control. A single application of dazomet killed almost 98% of the buried seed tested. Our research demonstrated that dazomet is an excellent tool for accelerating the depletion of a viable GRT soil seed bank. Further trials are planned to optimise dazomet rate and contact time, its effectiveness at destroying GRT seeds at different soil depths and how to incorporate these findings to successfully management GRT in the field.