Weed Density and Diversity under Two Weed Management Practices in Sloping Lands of Banana Plantation in Davao City, Philippines
Weed management in the slope farms of a banana plantation poses a challenge because the banana canopy provides a condition that allows weeds to proliferate, protecting fragile soil from erosion. If left uncontrolled, it could impair banana production. Manual weed removal disrupts soil structure that not only stimulates dormant seed germination but also increases soil erosion. Seedbanks, counts, dry weights, and diversity indices of broad-leaved weeds under two weed management systems (manual weeding and chemical weed control using cyclical application of paraquat and glyphosate) in a banana plantation were examined at two slope conditions: 15° and 25° inclination. Seedbanks at the start and six months after treatments yielded nine broad-leaved species of which three were dominant: Ageratum conyzoides, Bidens pilosa, and Cleome rutidosperma. While species diversity and seedling count from seedbanks were not significantly affected by weed management systems, the reduction in growth and abundance of the dominant species was achieved in chemical plots. Over ten regular observations in 13 months, there were consistently and significantly lower counts and dry weights of weeds in chemical plots than in manual plots. In addition, the shifts in weed population – from that dominated by noxious species to that composed of less noxious species – were achieved in chemical plots, which could have implications on the environment and the banana production. Regular monthly weeding can, within one year, reduce weed population to a level that could potentially impact soil erosion. To stabilize soil in sloping lands, weeding can be based on a threshold weed cover.