Abstract
No contribution of recently fixed NH4+ could account for the total increase of N-uptake by a maize crop at two planting densities during the first 30-day stage of crop growth at a 60 kg ha-1 level of N application; but considerable contribution to the total N-uptake by a maize crop was noted at a 300 kg N ha-1 level. Over the 60-day period of crop growth, a large portion of the recently fixed ammonium was utilized by the population of growing plants at both levels of N-fertilization to meet their N demand. Recently fixed NH4+ -N in high-fixing soils can be considered as conservation against loss from the soil.
