Thesis (BS Biology) -- University of the Philippines Mindanao, 2008

A sustainable weed management system in slopes should maintain a balance between the needs to protect the crop against competition from weeds and protect the integrity of the environment. Weeds have useful ecological functions so it is desirable to maintain a certain level of weed population in the farms but if left unmanaged, weeds can reduce crop yields. This report covers the first year of a long term experiment to compare the effects of two contrasting weed management systems on abundance and diversity of grass weeds in banana plantations in Mindanao, Philippines. The chemical weed management treatment consisting of paraquat and glyphosate applied monthly in a 3:1 fourth-month ration significantly reduce the count and biomass of five grass weed species compared to manual weed management, but it did not cause a decline in the seedbank. The Index of Dominance showed a tendency for the dominant noxious weed species to be replaced by less noxious species to be replaced by less noxious species, especially in areas where extensive colonization has not been established. On the other hand, the Index of Diversity showed that the use of chemical weed management treatment did not cause a decline in grass weed species diversity. Chemical weed management was 81% cheaper compared to manual weeding. The results imply that herbicides can be used in a sustainable weed management system that is also cheaper than that of the conventional manual-mechanical method