Hydrologic properties and leachate nutrient responses of soil columns collected from gypsum-treated fields

• Gypsum is increasingly being used as a soil amendment to improve crop production.
• Ca concentrations in soil profiles were significantly increased by gypsum application.
• Greater cumulative drainage in 4 and 12 yrs gypsum treated soils compared with controls.
• LT-gypsum may carbonates accumulate in subsoil and hydrologic properties are impeded.

Increased availability of flue gas desulfurization gypsum (FGDG) and the recognition of its potential to improve soil–water relationships have stimulated studies of its use on poorly drained soils with high seasonal rainfall, especially on no-tillage (NT) soils. Previous studies have focused on the effects of gypsum on hydrological properties at the soil surface (e.g. infiltration and soil crusting) but little information is available concerning the effects of surface-applied gypsum in profiles of non-sodic NT soils with contrasting drainage classes. To address this lack of information, undisturbed columns from two non-sodic NT soil profiles, characterized as being either moderately well drained or poorly drained, were collected from agricultural fields with historic information regarding number of years of gypsum application (i.e. 0, 4, and 12 yr). Alfalfa was planted in the columns and then plant growth, and soil chemical and hydrologic properties were measured. Higher Ca concentrations were found in both gypsum treated soils compared with control (CT) soils (P < 0.10). A greenhouse water balance study revealed significantly (P < 0.10) greater cumulative drainage (∼60%) associated with the Brookston long-term (LT) gypsum and the Celina short-term (ST) gypsum soil treatments than for the control treatments. This greater drainage response was attributed to Ca redistribution to lower depths and improved soil structure. However, restricted drainage in Celina LT columns was attributed to secondary Ca carbonate precipitation in pores at 60–75 cm depth. Leachate samples collected from the columns indicated no element deficiencies that would negatively affect alfalfa growth. Nutrients and trace element concentrations also were within accepted limits for good plant growth and water quality.