Farmer Participatory Evaluation of the Potential for Organic Vegetable Production in the Wetlands of Zambia

Abstract

Although wetlands (locally called dambos) are considered extremely vulnerable to poor agricultural practices, rising population pressures have caused their agricultural use to become increasingly important. Intensification of dambo use by way of chemical fertilizer and pesticide applications poses serious challenges to their ecological sustainability. This study evaluated gliricidia (Gliricidia sepium) leafy biomass as a possible alternative to commercial fertilizer, and Tephrosia (Tephrosia vogelii) leaf extract, commercial formulations of neem seed extract (Achook) and Bacillus thuringiensis (Thuricide) as alternatives to chemical pesticides in the production of cabbage in dambos. The study showed that soil fertility management practices can significantly influence the time to harvest the cabbage crop and its yield. Vegetables grown using gliricidia biomass produced significantly higher yields compared with the no-input option. The population density of diamondback moth (Plutella xylostella) larvae, the percentage of plants infested by cabbage webworm (Hellula undalis) and cabbage aphid (Brevocoryne brassicae) was significantly lower in cabbage treated with sprays of Tephrosia leaf extract and Achook. It is concluded that gliricidia leafy biomass as a soil fertility management practice combined with Tephrosia leaf extract and neem seed extract as a crop protection practice could increase the productivity of cabbage and ensure sustainable utilization of dambos.

Diamondback Moth, Plutella xylostella (L.) in Southern Africa: Research Trends, Challenges and Insights on Sustainable Management Options

“…Due to socio-economic challenges and high unemployment rates in SA [11], horticulture is fast transforming into an intensive production and high-income-generating enterprise [39,40]. However, despite large expansion in land committed to horticulture in the region, returns per unit land area are still minimal [41], mainly due to pest related losses and, in some cases, high production costs.…”

“…The lack of such policies in SA and the subsequent lack of regulatory frameworks account for the high pesticide residues in fresh products [2,42]. This is exacerbated by the cosmetic urban consumers' unconscious demand for damage-free brassicas [2,39,42]. The chronic nature of accumulated pesticide effect in humans makes the danger 'invisible' [63,64].…”

“…Farmers' perceptions and practices on the management of this pest in the region are not yet fully understood [39]. Research to date has been survey-based [5,20,22,40] and generalised on both insect pests and diseases for all horticultural crops.…”

“…On the other hand, African urban areas of the host DBM and evidence is presented that these traits may have coevolved, parasitoid efficacy in the face of climate change may be compromised [26]. Without coevolution of thermal tolerance, DBM challenge may likely intensify due to conducive climatic conditions [37][38][39][40][41] that may stimulate increased pest activity (feeding, breeding, and migration) [26,38]. Therefore, without efficient control mechanisms, the DBM problem could continue to increase despite the intensive pesticide use, which to-date may have been short-term, ineffective, unsustainable and expensive [18].…”

Greenhouse Gas Emissions from Intermittently Flooded (Dambo) Rice under Different Tillage Practices in Chiota Smallholder Farming Area of Zimbabwe

“…In many semi-arid to arid areas of Zimbabwe, dryland crop production has been decreasing because of perennial mid-season droughts which have been attributed to climate change. As a climate change adaptation strategy, smallholder farmers in Zimbabwe and southern Africa have been cultivating seasonal wetlands (dambos) [7,8]. Therefore, presently, dambos are a valuable resource for crop production due to their widespread occurrence; saturation and inundation for months during rainy seasons; and high fertility when compared to uplands.…”