Consider that one would like to introduce a certain type of pesticide in managing an annual crop pest or using a fertilizer for annual crop production. Would it be okay to calculate the NPV and IRR of this investment?

It is a bit unclear because all the costs are incurred in one season and the benefits are also got within the same season. If someone wants to grow the crops with the same pesticide next season, he or she has to incur those costs again and get the corresponding income, which are translated to benefits!!