The mean growth is the same with or without the additive. The mean growth with additive is bigger than without the additive. So we reject Ho. So we accept it. Plant growh is greater for additives added then for additives not added.
Average growth is different depending on the additive.
Reject the null. There is sufficient evidence to conclude that plant growth is greater with the additive than without the additive. There is a difference in the plant growth on addition of the additive with the standard fertilizer.