Making reoccurrence of aggressively invasive weeds irreversible through biochar

Background/Question/Methods

: From the biological invasion, the aggressively invasive plant species stand dominant and are extremely widely distributed in all diverse ecosystems at global scale. Most of the aggressively invasive plant species have common traits such as, wider ecological amplitude, quick life cycle, large seed bank, etc. Nevertheless, at a certain starting point of dealing with invasive plants in a highly infested area, there comes challenge of safer disposal or quarantine of the harvested mature biomass of the weeds having millions of viable seeds in it. Each of the biological, chemical, physical, and integrated pest management approaches used for control of aggressively invasive plants has its advantages, disadvantages, and severe limitations. Dealing with mature weed biomass having very high viable seed bank is a big challenge, especially through an approach that ensure zero probability of reoccurrence of weeds. The current study endeavored to achieve lowest reoccurrence probability of four aggressively invasive weeds viz. Broussonetia papyrifera. Parthenium hysterophorus, Cannabis sativa, and Lantana camara through pyrolysis of the harvested mature biomass and deriving weed biochar for its application in the infested area as a mean of reducing any further occurrence of weeds in the following seasons.

Results/Conclusions

: Subjecting harvested mature biomass with very high viable seed bank of the selected weeds as feedstock had resulted in four highly different types of biochar. Pyrolysis at 550oC with slow ramp rate rendered over for 3 hrs resulted in 100 % killing of the seed bank associated with the mature weed biomass. Weed biochar application back into the weed infested areas reduced germination, reoccurrence, total biomass, and total seed bank of each of the weeds; especially during first year of application. This perhaps was because of the volatile allelochemicals adsorbed on the surface of fresh biochar during pyrolysis at slow ramp rate. The succession of local grassland vegetation resumed in the fields that had history of severe infestation of weeds. This perhaps was because of alteration of soil nutrients and microbial communities caused by weed biochar application in the soil. The total ecological footprint of the pyrolysis-based management of mature weed biomass were significantly lower than physical, chemical, and biological methods of weed management. The study concluded that dealing with the mature biomass of aggressively invasive plant weeds through pyrolysis not only reduces reoccurrence of the weeds in the infested area but also create prospects of dealing with climate change.