Figure 1. Fluxes and concentrations of nitrate-N (pink), ammonium-N (blue) and amino acid-N (green) in the three soils under sugarcane.

Circle area is determined by the square root of pool size or flux. Mean pool size of 40 replicate flux measurements or soil extractions is shown inside each circle. Estimated I_max values (maximum estimated root intake rate) for sugarcane root uptake under fertilized and unfertilized conditions (nmol N cm⁻² h⁻¹ for nitrate, ammonium and glycine) are represented by dotted lines for comparison with fluxes. Free N pools (as determined by water extracts) and exchangeable N pools (as determined by KCl extracts) are shown in μmol N kg⁻¹ dry soil. For more detail and statistics see Table S1.