The influence of cultivation frequency on weed species composition and diversity in flood recession farming in the Okavango Delta, Botswana

Abstract

Introduction: Flood recession farming, locally known as molapo farming, is an important livelihood activity for the subsistence farming community around the Okavango Delta. The study was aimed at investigating the influence of cultivation frequency on non-crop species composition. It was carried out in the peripheral settlements of Shorobe, Makalamabedi and Lake Ngami. Methods: Vegetation sampling was conducted from March to April 2016 in 36 fields of varying historical cultivation frequencies. The cultivation frequencies were 5, 10 and 15 years with an uncropped control site. Sampling was done in 1-m 2 quadrats placed 10 m apart along a line transect. Shannon's diversity and equitability indices were used to compare diversity for each cultivation frequency within and across the study sites. The Kruskal-Wallis test was used to investigate significant differences in diversity between cultivation frequencies. Rank of abundance was used to determine the association of weeds with the cultivation frequencies.Results: Cultivation frequency did not influence species diversity (p > 0.05) at either Lake Ngami or Shorobe. Species evenness was significantly different (p < 0.05) between the cultivation frequencies at Shorobe, but not at either Makalamabedi or Lake Ngami. There was a significant difference (p < 0.05) in diversity indexes across the four cultivation frequencies. The 5-year frequency recorded the highest median score (Md = 1.352) while the 15-year frequency recorded the lowest median score (Md = 1.035). Corchorus tridens was the most abundant noncrop species at the 5-and 15-year frequencies. Cynodon dactylon was most abundant in the 10-year frequency while Cyperus esculentus was most abundant in uncropped fields. Conclusions: Cultivation frequency influenced weed species diversity and composition in flood recession farming. Flood recession farming fields were dominated by common weed species which are also troublesome in dryland arable farming. Uncropped sites were composed of wetland species that tolerate some dry periods or seasonal flood plains.

Impact of farming system practices on weeds in arable farmlands in University of Port Harcourt and environs, Rivers State-Nigeria

“…It could also be attributed for example that the weeds at seedling stage were very small at that time to be noted or the shoots could have been cut off as result of frequent weeding which was in line with the assertion of [42] that cultivation frequency influenced weed species diversity and composition in flood recession farming which were dominated by dry land arable weed species, while un-cropped or undisturbed site were composed of wet land weed species.…”

“…The result also revealed 78 of same weed species which occurred in wet and dry seasons respectively. These weed species which occurred in wet (rainy) and dry are attributed to the ability of weed species to overcome the impact of farming systems methods which were applied in the course of the cropping season for example frequent weeding, cultivation methods applied [42], cropping patterns, crop/weed species interactions, crop and crop cover effects and climate [43], multiple cropping and intercropping [44]. It has been recorded in literature that different cropping systems and weed management strategies have influenced weed infestation in today's agriculture as crop growers seeks ways to feed the growing population of the world.…”

Diversity and Allelopathic Potential of Weeds in Swampland

“…Excessive herbicide application might contribute to the ineffectiveness of controlling weeds and cause the spread of weeds (Salaudeen et al, 2022). Cultivation frequency also affects weed species diversity and composition in the Okavango Delta Botswana, where species diversity decreases with increasing cultivation frequency (Nthaba et al, 2018). Sawicka et al (2020) stated that the common weed population and its composition were affected by two major factors, including crop competition and soil seed bank, which depend on elements of the agrotechnology, such as crop rotation, tillage, sowing time and density, and cultivar choice.…”