Abstract

Vegetable production is an economically viable enterprise in Zimbabwe. The most commonly grown leafy vegetable is Brassica napus (rape). The productivity of this vegetable is affected by poor soil fertility, with nitrogen being the most limiting nutrient. An experiment was carried out to evaluate the use of two invasive weeds Lantana camara and Tithonia diversifolia as leaf teas on harvestable biomass production of rape. The experiment was laid out as a randomized complete block design with six treatments that included different leaf tea concentrations. Leaf length was shortest (12.11 cm) on rape that did not receive any fertilizer application but was similar for all other treatments. Leaf widths of rape treated with leaf teas were not significantly different at three weeks after transplanting. At four weeks after transplanting, rape fertilized with ammonium nitrate and T. diversifolia (7.5 â„“/week) had longest leaves. At five weeks after transplanting, rape that did not receive any fertilizer had the shortest leaves (12.79 cm) while ammonium nitrate gave the longest leaves. Highest rape fresh weight was from T. diversifolia (7.5 â„“/week) and AN treatments. Treatments that did not receive any fertilizer consistently produced the lowest leaf length, width and fresh weight. The study showed that yield of rape from application of T. diversifolia (7.5 â„“/week) was comparable to that of ammonium nitrate. Also, it is better to apply leaf teas than not to apply anything at all. Resource poor farmers who cannot afford to buy synthetic fertilizers could boost their rape production by using these leaf teas, and at the same time decelerate the spread of these weeds.

Key words: Brassica napus, leaf tea, Tithonia diversifolia, Lantana camara, smallholder farmer.