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Applications of ammonium nitrate (108 kg/ha application) and commercial inoculum (11.2 kg/ha) were made to the peanut (Arachis hypogaea L.) cvs. ‘Argentine’ (spanish) and ‘Florigiant’ (virginia) in 1978 and 1979. Both cultivars nodulated abundantly, even in the absence of inoculation, but plants of the cv. Florigiant were generally larger, yielded more, had a higher harvest index, and showed greater nodulation and higher N2(C2H2) fixation values than those of cv. Argentine. Inoculation did not increase plant weight or yield, though N2 fixation traits were improved in 1 year. Applications of nitrogen increased plant weight 49% in 1978 and 24% in 1979 and fruit yield by 37% in 1978 and 21% in 1979 but reduced harvest index from 37 to 34.9% in 1978 and reduced N2-fixing traits in both years. There is no evidence from this study to indicate any need for inoculation to peanuts in soils with high populations of the appropriate Rhizobium. However, the increase in plant weight and fruit yield with the application of nitrogen, although not economic, suggests that either the peanut-rhizobia symbiosis does not fix enough nitrogen for maximum yield or that fixed nitrogen is not utilized as efficiently as fertilizer nitrogen. |
