Nutrient Uptake Pathways for Corn

The three principal nutrient uptake pathways as reported by Barber (1995) are generally described as:

        1.     Root Interception – roots grow in a nutrient location

        2.     Mass Flow – nutrient moves with the soil water to the plant

        3.     Diffusion – nutrient movement is from higher to lower concentrations

The relative contribution for each nutrient uptake pathway for corn is shown in Table 1.

            Table 1                    Nutrient Uptake by Corn Roots__________________________

                                         _________% of Nutrient Uptake by Method_______
Nutrient                          Root Interception           Mass Flow                  Diffusion

Nitrogen                                     1                                 79                                20

Phosphorus                              3                                  5                                 93

Potassium                                 2                                18                                80

Most of the macronutrient nutrients move to the roots by either mass flow or diffusion.  For P&K, most of the nutrients move to the roots by diffusion.

The data in Table 2 compares the time it takes for P&K to move 1 cm. in two different soils in Indiana (Silborbush & Barber, 1983).

          Table 2            Travel Times for P & K Movement in a Soil__________________________

                                                    Time to Travel 1 cm.                       K Diffusion Rate, Expressed as a

                                                        P                      K                              Multiple of the P Diffusion Rate

                                                                                                                           times as fast as P

                                                       ———year——–                                       ———————
       Soil_   _

Raub Silt Loam                         3.45                 0.42                                                     8.1
Chalmers Silt Loam                1.89                 0.41                                                     4.6______________