Christoph Kessel, Nutrition (Horticulture) – Program Lead, OMAF & MRA

Keeping fertigated nitrate-nitrogen in the crop rooting zone is an important management strategy to ensure maximum uptake.  Nitrate-nitrogen is very mobile in the soil.  It can move with water out of the rooting zone and down through the soil profile.

The timing of the nitrate-nitrogen fertilizer injection during the irrigation event is key to keeping it in the rooting zone and available to plants.  Inject it too early and nitrate nitrogen can move beyond the rooting zone; injecting it too late means higher concentrations around emitters and uneven distribution in the root zone.

California researchers studied nitrate-nitrogen distribution from subsurface and surface drip systems in different soil textures¹.  The fertilizer was injected either at the beginning, middle or end of the irrigation event.

Their observations, shown in the figures below, demonstrate three important points to keep in mind…