Abstract:
N fixation and N transfer in maize/cowpea and sorghum/cowpea intercropping systems, as determined by
1SN isotope dilution technique was studied in two field trials conducted at Bata-atha, in the dry zone of Sri
Lanka. Two cvs. of cowpea Le; Bombay and MI-35 were used in maize/cowpea intercropping system, with
following combinations of treatments; maize/Bombay, maize/MI-35, Bombay (monocrop), MI-35
(monocrop) and maize (monocrop). A similar set of treatments was used in sorghum/cowpea intercropping
system also. The l5N atom excess, % Ndffa, total amount of N fixed, N yield and the total dry matter
production were estimated. Maize/cowpea intercropping resulted in an increase in total dry matter
production and total N yield compared to monocrop treatment. However the %Ndfa and total N fixed
showed a decrease compared to monocrop stand. The %Ndfa was 60-65% in monocrop while the same was
45-50% in intercropped treatments.
