The other step he could take was to pluck the spirit herbs and just throw them here and there while breaking the stems of those spirit herbs if possible.
Spirit herbs didn't lose their value even when they were plucked and weren't secured in a special jade casket.
So, plucking them and throwing wouldn't work, but breaking their stems would be enough to make them lose their value as their spirit qi would evaporate completely. It was similar to damaging the core of a cultivator.
The reason it wouldn't work was time. He wouldn't be able to pluck all these spirit herbs easily, and if it was a higher-grade spirit herb, possibly above Grade 7, then he wouldn't be able to break their stems with his strength.
The only possible way he could think of was poisoning the whole soil. He had knowledge of very strong poisons which could effectively poison the whole soil and the air around it.
