Leaching efficiency and plant growth response in an integrated use of saline water for coastal saline soil reclamation

Abstract

AbstractA field experiment was carried out to evaluate an integrated use of saline water for saline soil reclamation around Bohai Bay in China. A landscape shrub (Caryopteris × clandonensis 'Worcester Gold') was cultivated and irrigated with five water salinities (ECi): 0.8, 3.1, 4.7, 6.3, and 7.8 dS m−1. Drip irrigation was scheduled by evolving soil matric potential thresholds of −5, −10, −15, and −20 kPa in 4 years. A gravel‐sand layer as subsurface drainage was installed at 1.0 m depth. After 4 years, the extremely saline soil (ECe of 27.8 dS m−1) for 0–1.0 m depth was reclaimed to moderately saline soil (ECe of 4.1–7.2 dS m−1). The decreases in survival rate, growth, and shoot dry weight of the plants as increasing ECi were observed. To achieve a relative survival rate of >50%, the ECi thresholds for plants were 7.8, 6.9, 5.5, and 5.3 dS m−1 for the 4 years, respectively. The quantificationally estimating root zone drainage and salt leaching efficiency indicated that more efficient salt leaching offered by ECi up to 3.1 dS m−1 in comparison with freshwater with ECi of 0.8 dS m−1 and less efficiency occurred at ECi > 6.3 dS m−1. The plants strongly responded to the different soil water and salinity regime in the dynamic leaching process, as thus it is recommended to use an inter‐seasonal evolving matric potential threshold of −10 kPa for dry season of the third year, −15 kPa for rainy season and following dry season for providing optimized soil water and salinity condition.