Effect of gypsum on exchangeable sodium percentage and electrical conductivity in the Daeho reclaimed tidal land soil in Korea—a field scale study

Abstract

A reclaimed tidal land along the shore has poor soil properties such as high exchangeable sodium percentage (ESP), and electrical conductivity (EC) due to excess sodium (Na) content. Therefore, Na content should be decreased to improve the land productivity, and for this, gypsum has been widely used. The objective of this study was to determine the changes in ESP and EC of the gypsum-treated reclaimed tidal soil in a field scale. For this, gypsum was applied to Daeho reclaimed tidal land (500 ha) in Korea for 5 years (2006 to 2010). The Daeho reclaimed tidal land has been used as reclaimed paddy fields since 1993. The application rate of gypsum was calculated based on exchangeable calcium (Ca) contents and soil cation exchange capacity (CEC) to maintain 60 % exchangeable calcium percentage (ECP) of CEC in soil and the average amount treated was 1570 kg ha−1 year−1. The changes in ESP and EC were monitored from 2006 to 2010, and 2013. The ESP dropped from 80 % in 2006 to 34 % in 2013. The EC of the soil was decreased by 73 %, from 11.5 dS m−1 in 2006 to 3.1 dS m−1 in 2013. Eventually, it was estimated that the ESP will be lowered below 15 % in 2023 with continuous treatment of gypsum according to ECP calculation, and EC will be declined to reach at 0.5 dS m−1 in 2035, the average EC level of Korean rice paddy. This field scale study evidenced that gypsum application effectively improves the soil properties of reclaimed tidal soil by decreasing ESP and EC.