The effect of farmyard manure and nitrogen fertilizer on vegetative growth, leaf yield and quality attributes of Solanum villosum (Black nightshade) in Keiyo district, rift valley

Abstract

The African Leafy Vegetables (ALVs) are particularly important as adjunct accompaniment to the staple cereal foods such as the East African corn meal (ugali). In order to increase productivity and utilization of these ALVs, there is needed to develop suitable agronomic practices suited for farmers in specific agro-ecological zones. A study was carried with an objective of determining the effects of various levels of Farmyard manure and Calcium Ammonium nitrate (CAN) on vegetative growth, yield and quality (Vitamins A & C, Nitrates) of Solanum villosum in Keiyo district, between long rains and short rains of Year 2002. Effect of prolonged cooking by the Keiyos on vitamin A and C as well as anti-nutrient (nitrate) content of this vegetable was also determined. The experimental layout was a RCBD with four replicates. The treatments were four levels of organic manure (5, 10, 15, 20 t/ha) and four rates of nitrogen fertilizers (100, 200, 300, 400 kg/ha). The addition of various rates of organic and inorganic fertilizers that were tested significantly improved vegetative growth and increased leaf yields of Solanum villosum (p<0.05). The yields obtained from plants grown with organic manure were generally higher than from those with inorganic fertilizers. The incorporation of either organic or inorganic fertilizer increased Vitamin A content especially in older (14 week) tissues during both seasons. The organic manures at high levels (20t/ha) increased, while application of C.A.N at 200-400 kg/ha decreased Vitamin C content in both young and older tissues. During the first season, application of both organic and inorganic fertilizers decreased the accumulation of nitrates in young tissues. Traditional methods of boiling the ALV’s for long significantly reduced vitamin A and C and nitrates content. In all experiments, the farmer’s crop, though better than the controls, were comparable to low fertilizer levels, in all attributes determined. In conclusion the quality attributes of Solanum villosum was influenced, significantly, by the kind and rate of fertilizer applied, the season of growth, plant age, farmer’s agronomic practices as well as cooking.