USE OF VERMICOMPOST AS A SOIL SUPPLEMENT ON GROWTH AND YIELD OF RAPE (Brassica napus)

Rape (Brassica napus) is an important and widely grown vegetable crop for food and income generation in most homesteads around Zimbabwe. Most households in Zimbabwe use inorganic fertilizers to improve production of rape in sandy soils which in turn are robbing the soil of its fertility. The present study investigates the effects of vermicompost as a soil supplement on growth and yield of rape compared to chemical fertilizers. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. A set of different vermicompost treatments (2.1%, 4.2%, 8.0%, 12.5%, and 12.5%) and inorganic fertilizer treatments (0.25%, 0.33% and 0.4%) were compared. Results revealed that the inorganic fertilizer treatments favored the growth and yield of rape more than vermicompost treatments. The inorganic fertilizers had quicker rate of release of nutrients as well as higher level of plant available nutrients. Likewise, the number of leaves, leaf length, number of marketable leaves, fresh yield mass, leaf width and whole length was also significantly better in case of inorganic fertilizer treatments. Generally, all treatments varied (p<0.05) as the growth progressed. There was significant interaction (p<0.05) between the treatments at 10 day intervals which was expressed in cumulative number of leaves and number of marketable leaves. It was concluded that use of vermicompost alone as a soil supplement in sandy soil for production of rape lead to lower growth and consequently yield responses. Hence the sole use of vermicompost as soil supplement should be discouraged and an integrated nutrient management plan may be evaluated as the most logical solution.