Irrigation well water in Nebraska: essential nutrient contents and other properties

Water nutrient concentrations and other properties were surveyed by
sampling water from 642 irrigation wells in Nebraska. The amount of Ca,
Mg, S, Cl, and B applied in irrigation exceeds removal in 15 Mg ha-1 of
corn (Zea mays L.) grain harvest for most wells. Irrigation supply
exceeded corn grain harvest removal of K, Mn and Mo for >20% of the
wells. The supply of P, Zn, Cu, Fe, and Mo was generally very low but
sufficient with some wells to be considered in nutrient management plans.
The median level of nitrate N was 4.4 ppm with 25% of the wells having
>10 ppm NO3-N which is above the suitability limit for human
consumption. The agricultural lime equivalent applied with one or two ML
of irrigation was enough to neutralize the acidifying effect of 200 kg
ha-1 of fertilizer-N for 70% or 89% of the wells. Nutrient and lime supply
was relatively low for Sandhills wells and relatively high for wells in
river valleys of <100 ft depth. No wells had excessive Na levels
but 0.3% of the wells had salinity levels of concern. A grouping of wells
into 11 aquifer, geological formation and well-depth combinations
accounted for >20% of the variation for most water properties but
much variation occurred within groups. Sampling of the well water is
needed for full optimization of nutrient and soil management. Information
on nutrients supplied through irrigation should be complemented by regular
soil testing and the use of recommended nutrient management guidelines.