Effects of 15N-nitrate fertilization on yield and dinitrogen fixation in common bean (Phaseolus vulgaris L.)

Abstract

The isotope dilution method was used to examine the influence of ¹⁵N-nitrate fertilizer on dinitrogen fixation and dry matter production in young common bean (Phaseolus vulgaris L.) plant in a phytotron experiment. There were slight variations in dry matter yield with significantly different N concentrations of the bean crop in response to fertilizer nitrogen applieation. The proportion of total N derived from N₂ fixation in the vegetative plant parts decreased from 43.5 to 4.7 per cent as the rate of fertilizer nitrogen increased from 0 to 150 kg N/ha. However, the degree of inhibition of N₂ fixation by applied nitrate-N was not different at the 75 and 150 kg N/ha rates. Inoculation did not affect the relative contributions of fertilizer and soil nitrogen to total shoot N at the 75 and 150 kg N/ha levels.