Effects of Organic Nitrogen Sources on Growth, Leaf Yield and Nitrate Content of Swiss Chard (Beta Vulgaris Var. Cicla)

Abstract

Swiss chard (Beta vulgaris var cicla) is one of the most valuable leafy vegetable that is widely adapted and the most nutritive exotic vegetable. However, it tends to accumulate more nitrates than other leafy vegetables. The nitrates may be converted to nitrite causing infantile methaemoglobinaemia, carcinogenic nitrosamines and even teratogenesis. Swiss chard grows well in organic fertilizers and has less nitrate accumulation. However, there is limited information on the specific type of organic fertilizer to use in order to reduce the amount of nitrate level in Swiss chard. The study was conducted to determine the effects of organic sources of nitrogen on growth, leaf yield and nitrate content of Swiss chard in Kericho County. The treatments consisted of chicken manure, goat manure, cow manure, control and Calcium ammonium nitrate (CAN). The experiment was laid out in a Randomized Complete Block Design with 3 replications. Data was collected on five randomly selected plants per treatment. The variables measured included plant height, number of leaves, leaf length and width, which was done weekly for a period of 8 weeks after transplanting. The plant survival, root and shoot fresh weights were determined on the 8th week after transplanting. The collected data was subjected to analysis of variance using GenStat statistical software and the means separated using Least Significance Difference at α = 0.05. Poultry manure had the highest plant height, leaf number, width and length, survival and shoot fresh weight than the other treatments. Root fresh weight was high in CAN treated plants than the other treatments. The CAN treated plants accumulated two times more nitrate than poultry manure treated plants. Among the organic nitrogen sources goat manure accumulated less nitrate than poultry and cow dung manures and this was related to the nitrogen content of the manures. Supplementing goat manure with poultry manure may increase the growth and yield of Swiss chard while maintaining the nitrates at a lower level.