Fig. 3.

Soil ammonium oxidation rates (mg of NO₂⁻ N per kg of soil per day) in field plots planted with tropical pasture grasses (differing in BNI capacity) and soybean (lacking BNI capacity in roots) [over 3 years from establishment of pastures (September 2004 to November 2007); for soybean, two planting seasons every year and after six seasons of cultivation]. CON, control (plant-free) plots; SOY, soybean; PM, P. maximum; BHM, Brachiaria hybrid cv. Mulato; BH-679, B. humidicola CIAT 679 (standard cultivar); BH-16888, B. humidicola accession CIAT 16888 (a germ plasm accession). Values are means ± SE from three replications.