Irrigation Water Quality, Soil Amendment, and Crop Effects on Sodium Leaching

Authors:
  • JBJ. W. Bauder
    J. W. Bauder
  • TBT. A. Brock
    T. A. Brock
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Abstract
Due to prolonged irrigation with water of marginal quality, salination of irrigated soils in some areas of southeastern Montana has led to a need for better understanding of the soil and water management alternatives for irrigators. A study was conducted with Haverson silty clay ( fine-loamy, mixed, calcareous, mesic Ustic Torrifluvent ) to determine the effect of combinations of chemical amendments, crop species, and irrigation water quality on Na + and salt leaching from saltaffected soils. Amendments included CaSO 4 , P-CaSO 4 and MgCl 2 ; also included was a nonamended control treatment. Crops included alfalfa ( Medicago sativa L.) , barley ( Hordeum vulgare L.), sorghum-sudangrass [( Sorghum vulgare 2 Sorghum drumondii ) (sordan)] ,and a noncropped control. All soil columns (0.15 m 2 0.5 m) were irrigated with either high Na + adsorption ratio (SAR adj = 16.6) , high total dissolved solids (TDS = 1647 mg L -1 ) water, or low SAR adj (1.15), low TDS (747 mg L -1 ) water. Drainage volume, electrical conductivity (EC), SAR, Na + of drainage water, and Na + leaching were monitored over three crop cycles. Irrigation with high SAR-high TDS water increased the soil solution EC to approximately 5.5 dS m -1 , but did not decrease crop yields relative to irrigation water having SAR adj and TDS of 0.37 and 747 mg kg -1 , respectively. Magnesium displaced Na + on the exchange complex, but the effects were short-term compared to CaSO 4 or P-CaSO 4 . Amendments increased yields of barley from 14%-27% and alfalfa by 25% but had no effect on sordan. Columns cropped to barley had 28% greater Na + leaching than columns planted to other crops. Noncropped columns accumulated the least net soluble salt and Na + . Results of this study demonstrate that specific crop and amendment combinations can significantly affect the efficiency of saline soil reclamation strategies and impact quality of irrigation return flow.