Evaluation of Moringa (Moringa oleifera (Lam) as a shade tree for Rape production in the Lowveld Semi-Arid region of Zimbabwe
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Rape (Brassica napus) is the most popular vegetable in semi-arid region Zimbabwe owing to its nutritional value and income generation. This leafy vegetable is a cool-season crop and its production is limited to periods of low temperature especially in the semi-arid region of Zimbabwe, which is characterized by hot dry conditions during hot season. Since rape production is difficult due to high temperatures, excessive radiation, and disease prevalence among other causes, production under tree shade can assist by modifying the microclimate. A factorial experiment was carried out at Chiredzi Research Station in the 2006/7 rainy season to study the effects moringa shade on rape vegetable grown in March and June. Pruning consisted of two levels: pruning and no pruning while, cropping system consisted of sole moringa and moringa/rape intercrop. Two factors were considered, cropping system (moringa/rape intercrop and sole moringa) and pruning (pruning and no pruning of moringa).The control treatment was sole rape (control). Moringa shade reduced rape dry weight in the moringa/rape mixture for both March and June rape crops by 35.9 % and 60.6 % respectively. Pruning moringa coupled with low moringa height significantly increased rape dry weight by 7.3 % in the moringa/rape mixture for the March crop. The negative effect of reduced rape yield was moderated by pruning moringa to reduce its height. Rape/moringa stands led to the reduction in weed densities and weed biomass, and at the same time increased gravimetric moisture levels. Based on these results rape/moringa mixtures are recommended as they are more productive, giving greater biomass outputs than sole rape. These conclusions are based on March to June tests hence assessments for the July to February are recommended.