Where a treatment is needed in different kinds of situations, each kind of treatment may need replications. Using replications and organizing results from many trials builds more understanding and confidence than trying a treatment only once or twice. Differences in response between two treatments across two types of sites, may suggest that some of the weed management units used for planning should be split so that each new unit gets the planned treatment most effective for that type of site. If you have difficulties with these statistical concepts you might want to talk with someone who is more familiar. Your local Cooperative Extension office also has available additional information.
Life is full of lessons.
We tend to face the same lessons over and over again until we learn from then. Then we move on to more interesting lessons. However, sometimes we face more difficult lessons because we didn't learn the easier ones. Today we face a crisis in most of the West because we were slow to learn lessons for successful prevention of weed invasion. The crisis got worse and the lessons more difficult when we failed to learn the lessons for locating and eradicating every first weed of each invasive species.