Ipomoea weed is a creeping annual herb, widespread in the semi-arid districts of Southern Kenya, which colonizes and spreads rapidly immediately after the onset of the rainy season (Mganga et al., 2010a). The species is mainly found in disturbed or degraded sites. The plant exhibits most characteristics common to invasive species, which include capacity for rapid growth and so expansion, capacity to disperse and reproduce widely or by nurturing fewer progeny but with great efficiency (Emerton and Howard, 2008). The species also capable of effective competition with local species for food, space, light and water. Mostly, Ipomoea spp. weeds are found in lowlands although they can also be found in the fairly sloppy lands. The onset of rains normally leads to resprouting of the seeds that are dispersed over the season upon drying. This species is reportedly a recent rangeland pasture colonizer weed in Kajiado County.
This species has characteristic prolific growth, beautiful inflorescence, heavy seeding ability, heavy foliage, well spread and developed root system, aggressive natural pasture competitor, smothers natural pasture in its proximity, not palatable to livestock and highly responsive to even a marginal rainfall regime. The weed can grow to a height of more than 2 meters and one stool can spread up to 4meters in diameter.
The weed has invaded and colonised over one million acres of rangeland and is expanding year after year. The weed was noted to be the most problematic in the study area since it engulfs and covers the newly established grass stand.
Fresh and heavy biomass of Ipomoea has been reported to suppress the growth and development of the grasses underneath it resulting in high incidences of grass seedling mortality. This is through deprivation of sunlight necessary for normal photosynthetic function. The net effect is the poor establishment of grasses with much of the denuded areas remaining bare after the end of the rains (Mganga et al., 2010b).
Pastoralists livelihoods is entirely depended on livestock therefore pasture availability remains a very important aspect for their survival. Although the persistent long droughts have become frequent due to effects of climate change and variability, Ipomoea weed which colonizes pasture fields have also played a significant role in pasture depletion in Arid and Semi-Arid Lands (ASAL) areas.
Also, pasture production and preservation is identified as one of the mitigation practices to climate change effects such as the frequent droughts, but the presence of this invasive weed limits maximum potential of biomass productivity. Therefore, without addressing the invasive weed first pasture will remain unavailable for livestock among the pastoralists of Kajiado County.
The study seeks to manage the weed through mechanical uprooting of the weed to evaluate if there will be any significant change in terms of increase in biomass productivity and emergence of vegetation species diversity.
The findings will then help the community in understanding if the mechanical management of the weed has any significant impact on biomass productivity to help them in mitigation of recurrent droughts.