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.
