Biostimulants Do Not Mitigate the Effects of Pasture Dieback in the Australian Wet Subtropics

Pasture dieback is a disorder that causes the deterioration and death of susceptible tropical grass pastures in Eastern Australia. Previous reports from the Australian dry subtropics have suggested that biostimulants may be effective in mitigating the effects of pasture dieback. In this study, in two experiments (1 and 2), biostimulant products were applied to dieback-affected pastures, and pasture growth biomass and nutritional attributes (neutral detergent fiber and crude protein) were assessed 30 days after application compared to a control (water application only) treatment. In a third experiment (exp 3), biostimulant products were applied to a pasture prior to dieback incursion, and plant symptoms were assessed 16 days after application. In experiments 1 and 2, after 30 days, there was no significant difference in biomass production or nutritional attributes between any biostimulant treatments and the control, with mean biomass yields of 471 ± 61 kg ha−1 at site 1 and 1371 ± 78 kg ha−1 at site 2. In experiment 3, plant dieback symptoms progressed evenly across all plots, with no significant effect between treatments 16 days after treatment application. There was no evidence that the tested biostimulants were effective in preventing the spread of dieback or improving pasture recovery from dieback.