Check out our new paper in Scientific Reports comparing soil nitrogen fluxes with plant nitrogen uptake capacity: http://www.nature.com/articles/srep15727.
We took a microdialysis system (and a shady tent) down to Jacob’s Well, Queensland, and measured soil nitrogen fluxes in three sugarcane fields. We compared a recently urea-fertilised field, an organic-fertilised field, and an unfertilised field.
For the first time, we compared these soil nitrogen fluxes with root nitrogen uptake capacities for nitrate, ammonium and amino acids (which we determined in a linked experiment). We discovered that nitrogen supply far exceeded root uptake capacity (per unit surface area) in both fertilised fields – this means that the excess nitrogen cannot be accessed by the crop, and is vulnerable to loss. By contrast, the unfertilised field supplied nitrogen well below the plant’s uptake capacities.
This demonstrates the need for better temporal matching between fertiliser supply and crop nitrogen demand.