Micromorphology of Gypsum Amended Soils From NO-till Fields in Ohio, USA.

Gypsum has been used extensively in reclamation of sodic soils with infiltration problems, and it is well known that it improves soil physical condition by promoting flocculation (compression of the double layer allowing coagulation into microaggregates), enhancing aggregate stability, and increasing the infiltration rate. In the field; flocculation is a necessary condition for the formation and stabilization of soil structure. However, positive effects on the physical properties of the whole soil profile (surface and subsurface horizons) of non-sodic soils are not well studied in the Midwest US, where sodic soils and salinity problems are uncommon, though, many farmers currently apply gypsum to non-sodic soils, and the use of by-product gypsum as an agricultural amendment is increasing. In addition, few studies have analyzed structural effects of gypsum in subsurface horizons of non-sodic soils, especially in the root zone. The purpose of this study was to determine and compare structure, porosity, and pore size distribution in the whole soil profile of two soils with different drainage class: Brookston (poorly drained) and Celina (moderately  well drained), three gypsum application rates: control, shorter application (3 years) and longterm  application (12 years) in no till-fields. Structural effects were explored with the preparation and utilization of thin sections to describe micromorphological characteristics on soil from the lysimeters. Undisturbed soil samples were obtained at seven depths (0-5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-40 cm, 40-60 cm and 60-74 cm), from vertical and horizontal faces of six lysimeters (30.5 cm of diameter and 74 cm long) using circular tins of 6 cm diameter and 2.5 cm height. Objective information is needed on which to base rational decisions about gypsum application to non-sodic soils.