Crop Species, Amendment, and Water Quality Effects on Selected Soil Physical Properties

Abstract

AbstractSaline and sodic soils have developed in some irrigated areas of Montana. Cropping systems that promote maximum efficacy of surface‐applied amendments for reclamation need to be identified. Effects of crop species, amendment, and water quality on alteration of selected physical properties of a Haverson silty clay (fine‐loamy, mixed [calcareous], mesic Ustic Torrifluvent) were compared. Crops grown in lysimeters and compared with a noncropped control were alfalfa (Medicago sativa L.), barley (Hordeum vulgare L.), and sorghum‐sundangrass [Sorghum bicolor (L.) Moench‐ S. × drummondii (Steudel) Millsp. & Chase], commonly referred to as sordan. Soil amendments included a check, gypsum (CaSO4·2H2O), phosphogypsum (CaSO4·2H2O with <1% [w/w] P), and MgCl2. Lysimeters were irrigated with water having either a total dissolved solids (TDS) concentration of 0.75 g L−1 and a sodium adsorption ratio (SAR) of 1.15 or TDS of 1.65 g L−1 and SAR of 7.01 until three barely crops were successively grown. The presence of a crop caused a significant increase in bulk density in all lysimeters and a significant decrease in total porosity, compared with the uncropped control treatments. Barley caused the greatest decrease in total porosity, followed by alfalfa, then sordan. Total porosity decreased nearly 0.1 m3 m−3. The result was a significant increase in number of micropores (<0.149 × 10−2 mm radius) and a disproportionately greater decrease in number of macropores (>1.49 × 10−2 mm radius). Soil water release characteristics differed among the different crop treatments. Neither amendment treatment nor irrigation water quality had a significant effect on either porosity, pore‐size distribution, or bulk density. Results of this study indicate that crop selection and rotation may affect the significance of surface‐applied amendments used for reclamation and leaching of Na‐ and salt‐affected soils.