Effect of gypsum and rice straw compost application on improvements of soil quality during desalination of reclaimed coastal tideland soils: Ten years of long-term experiments: Ten years of long-term experiments

The objective of this study was to investigate the effectiveness of applying gypsum and rice straw compost on improvements in soil quality during the desalination of previously reclaimed coastal tideland soils. The four treatments were control (without amendment), gypsum, rice straw compost, and gypsum + rice straw compost. The experiments were carried out in a completely randomized design with three replicates. Saturated electrical conductivity (EC_e) and exchangeable sodium percentage (ESP) values of soils treated with gypsum, or gypsum + rice straw compost, reached the salinity and sodicity classification limits of 4 dS m^{− 1} and 15% (US Salinity Laboratory Staff, 1954), respectively, after eight years of leaching experiments. However, despite 10 years of leaching experiments, neither the control nor the rice straw compost alone treatment reached the salinity and sodicity classification limits. The addition of gypsum and rice straw compost resulted in a reduction in soil bulk density and a corresponding increase in soil porosity in highly saline-sodic soils (p ≤ 0.05). The results of mean weight diameter (MWD) showed that the application of soil amendments increased MWD significantly (p ≤ 0.05); the highest MWD was observed for the gypsum + rice straw compost treatment and was twice the magnitude of the control.