Influence of Flooding Pattern on Weed Species Diversity and Maize Yield in Flood Recession Farming in the Okavango Delta, Northern Botswana.

Flood recession farming, locally known as molapo farming is a significant livelihood for the riparian communities that live along the Okavango Delta. However, this system is threatened by variability in flooding patterns which influence weed diversity and crop yield. This study aimed to determine the influence of flood patterns on weed species diversity and maize yield in molapo farming. Vegetation sampling was conducted in twelve fields across two flooding patterns: lake flats and saucer-shaped. A line transect with squared-meter quadrats spaced 10 meters apart was used to sample weeds. Each field’s center row had four square-meter quadrats that were systematically spaced five meters apart to collect samples of weed and crop biomass. The weed and maize biomass in each quadrat were then oven-dried for 48 hours at 80°C. The Shannon diversity index and species richness for each flooding pattern were determined using Paleontological Statistics version 3.12. The most abundant weed species in the saucer-shaped flooding pattern was Cyperus esculentus with a density of 110,967.74 while in the lake flats, Sida cordifolia was the most abundant, with a density of 144,459.46 individuals ha⁻¹. The weed species diversity and evenness of weed species were 2.60 and 0.67 in saucer-shaped and 2.13 and 0.50 in lake flat flooding pattern, respectively. Lake flats produced two times higher maize biomass than saucer-shaped flooding pattern. These findings indicate that flooding patterns influenced weed species diversity, which in turn affect maize yield. Further, they imply that flood dynamics and weed species diversity should be considered when developing weed management strategies to improve maize yield in flood recession farming.