Irrigation well water: Essential nutrient contents and other properties
Wortmann, Charles S.
Water nutrient concentrations and other properties were surveyed by sampling water from 642 irrigation wells in Nebraska. The amount of Ca, Mg, S, and Cl 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, B, 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 mg kg–¹ with 25% of the wells having >10 mg kg–¹ NO₃–N, which is above the suitability limit for human consumption. The agricultural lime equivalent applied with 1 or 2 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 <30.5 m (100 ft) depth. No wells had excessive Na levels but 0.3% of the wells had high salinity levels. A grouping of wells into 11 aquifer–geology–depth categories accounted for >20% of the variation for most water properties but much variation occurred within categories. Sampling of the well water is needed for optimized 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.
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