Biological nitrogen fixation activity under clover-grass mixtures.

Dinitrogen fixation activity was determined directly on experimental plots in mixtures of grass with red and white clover in the year of sowing as well as in the first year of full utilisation using the method of acetylene reduction (ARA). Furthermore, numbers of bacteria, actinomycetes, fungi and Azotobacter sp. were determined in soils under the experimental mixtures.