Abstract:
Kale (Brassica oleraceae var acephala) is green leafy vegetable rich in vitamins and minerals.
Management of nitrogen fertilizer has a direct effect on the aphid infestation of kales. Therefore,
this research study has helped to establish appropriate nitrogenous fertilizer rates and application
regimes so as to improve kales production and yields hence improving people’s nutrition and
enhancing food security in Embu County. A field experiment was carried out in University of
Embu greenhouse. The research was conducted as from January to March, 2019, to study the effect
of different rates of nitrogenous fertilizers application on aphids’ infestation and yields of kales
leading to low yield. The nitrogenous fertilizer was bought from an agro vet. The rates of
nitrogenous fertilizers which include: 0 kg N/ha, 193 kg N/ha, 386 kg N/ha and 772 kg N/ha were
evaluated with respect to the population of aphids. Kale seedlings were raised in a nursery and
then transplanted to the greenhouse at a spacing of 30cm by 45cm with three replications.
Randomized Complete Block Design method was used in the field. Data was collected three weeks
after transplanting and introduction of aphids and continued for a period of 5 weeks. Data collected
was on aphid population and yields, and was analyzed using ANOVA. Means was separated using
LSD at 95% confidence level. From the results obtained, the mean incidence of aphids increased
as nitrogen level increased which was significantly different among plants receiving different
levels of Nitrogen. High levels of N application (772 kg N/ha) recorded significantly higher
incidence of aphids and the same was also observed in mean yield. Therefore, Use of the optimum
amounts of N in kale production is important for boosting vegetative growth and reducing its
infestation by aphids hence reducing losses.
