Table 2: Transport, sorption, and root parameters used in the NST 3.0 model to describe P uptake by switchgrass for the 0–120, 0–30, 30–60, and 60–120 cm soil depths.

ParameterUnits0–120 cm0–30 cm30–60 cm60–120 cm

Diffusion coefficient in watercm2 s−1
ΘVolumetric soil water contentcm3 H2O/cm3 soil 0.37 0.39 0.36 0.36
Impedance factorUnitless 0.42 0.45 0.40 0.40
Water uptake at rootcm s−1
Initial solution concentration mol cm−3
Buffer powerUnitless 63 47 74 69
Maximum influx at high concentration mol cm−2 s−1
Solution concentration when influx is 0.5  mol cm−3
Solution concentration when influx is zero mol cm−3
Root radiuscm0.0090.01210.00750.0085
Half distancecm0.3040.1980.2270.489
Initial root lengthcm m−34,162,6211,935,5081,371,549855,564
Root growth ratecm d−18,48410,50610,3064,641

From Edwards and Huffman [18].