Factors affecting nitrogenase activity (C2H2 reduction) associated with sorghum and millet estimated using the soil core assay

Abstract

Factors affecting nitrogenase activity associated with sorghum and millet roots have been studied. Plants grown in iron cores in the field and then assayed had significantly higher activity than plants cored at the time of assay. Mechanical disturbance during transportation of the cores reduced the activity significantly. Any delay between cutting off the plant top and injecting C2H2 gas led to a reduction in the level of nitrogenase activity determined. Diurnal variation in nitrogenase activity was noted but was not correlated with soil temperature. Most activity occurred at the end of the photoperiod. Seasonal variation in nitrogenase activity of plants was observed and was correlated with the ontogenetic development of the host plant, being most at flowering. A low but significant correlation existed between soil moisture content and nitrogenase activity associated with the plant.