| dc.description.abstract | A field experiment was conducted at the University of Nairobi, Kabete Field Station
between April, 2000 and March 200 1 to determine the effects of nitrogen source (organic,
inorganic or combination) and rhizobium inoculation on growth, biological nitrogen (N)
fixation (BNF) and yield of green grams (Vigna radiata (L.) Wilczek). Nitrogen was applied
at a rate of 100 kg N/ha as calcium nitrate (Ca(N03)2), urea, chicken manure (CM), 50 kg
Nlha Ca(N03)2 + 50 kg N/ha CM, 50 kg N/ha urea + 50 kg Nlha CM and no N application.
The grams were either inoculated or not inoculated. Wheat was grown as reference crop to
determine BNF by difference method. The experiment was laid out in randomized complete
block design with three replications.
The results showed that total, leaf and stem dry matter, leaf area index (LAI), solar
radiation interception, root nodulation, biological nitrogen fixation (BNF) and seed yield were
significantly influenced by N sources. The numbers of leaves/plant, branches/plant,
seeds/pod, harvest index (HI) and 1000-seed mass were not significantly affected by N
sources or rhizobium inoculation., Ca(N03)2 application increased total dry matter (TDM,
g/m"), photosynthetically active radiation (PAR) interception and LAI and seed yield relative
to other N sources. Nodulation and BNF were significantly increased by rhizobium
inoculation but were reduced by fertilizer N application. Nitrate N source gave the highest
economic returns but was more costly to purchase. Chicken manure led to high economic
losses due to high cost of buying the manure and low seed yield observed. The gross margin
increased 6.5 times in plants that were inoculated with rhizobium without fertilizer N
application, compared to non-inoculated. Farmers with limited financial resources could use
Rhizobium while those not limited by finances may use nitrate N source to increase profits in
green gram production. | en |
