Dynamics of mineral nitrogen in soils supporting potato crops

Following application of fertiliser-N to the seedbed of potato crops, concentrations of extracted mineral-N were up to 3 times greater than would be anticipated by calculation. The rates at which both NO₃^–-N and NH₄⁺-N apparently appeared and disappeared in the soil solution were, at various times, also much greater than could be attributable to any transformations resulting from microbial activity. This suggests that the involvement of other factors in this phenomenon must be considered. The effect of certain physical parameters such as water movement, resulting from capillary action and evaporation from the soil surface, may be implicated. We suggest that soil microbes are not directly involved in the early fate of fertiliser-N, primarily due to C-limitation in arable soils. N dynamics in fertilised potato systems require further studies targeting the relationships between nutrient concentrations in soil solution and mass flow of soil water.