02267nam a2200265 a 450000100080000000500110000800800410001910000180006024500690007826000810014730000100022849000230023850000470026152015450030865000160185365000090186965000100187865000090188865000140189765300080191165300080191965300360192765300290196365300090199216216731996-01-29       1980    bl uuuu  m   00u1 u    #d1 aBODDEY, R. M.  aBiological nitrogen fixation in the rhizosphere of lowland rice.  aTrinidad: Faculty of Agriculture, University of the West Indies, Marcoc1980  a275p.  aTese de Doutorado.  aTese de Doutorado. Orientada por: N.Ahmad.  aAn acetylene reduction technique was developed for estimating in situ the nitrogenase activity in the rhizosphere of lowland rice. The technique involves the use of only cheap and lighweight equipment, and is quick to set up. A comparison of this technique with the excised root assay, revealed little correlation of the results. This was attributed to the artifacts introduced by the long pre-incubation in the latter technique, including a 40 fold increase in the numbers of nitrogen-fix ng bacteria this period. Comparisons of the nitrogenase activity in the rhizosphere of different tice varieties at the same growth stage on different soils revelead very little differences between varieties or soils, especially when activity was expressed per unit weight of plantNitrogenase activity per plant was maximal at the flowering and early grain filling stages, but when the data was expressed per unit weight of plant, young plants had the highest activity. Increased temperature caused increased nitrogenase activity, but at constant temperature there was little diurnal flucutation in activity caused by the presence or absence of light. Estimates of the quantity of nitrogen fixed during the entire cropping season based on data from the in situ acetylene reduction assay indicated that the input did not exceed 6 kg N.ha-1. It is possible however, that the in situ technique used does not detect much of the nitrogenase activity in the soil some distance from the root (the outer rhizosphere). Nitrogenase activity in the rhizosphere..  arhizosphere  arice  aArroz  aRaiz  aRizosfera  aBNF  aFBN  aFixacao Biologica de Nitrogenio  aNitrogen fixing bacteria  aRoot