Soil salinity at reclaimed tidal land in Korea is highly variable and depending on soil characteristics and weather conditions. The objective of this study was to evaluate the temporal changes on soil salinity and the relationships between soil salinity and salinity parameters in reclaimed tidal lands. Soil samples were periodically collected at 0 - 20 cm (surface) and 20 - 40 cm (subsurface) layer at Saemangeum (sandy loam) and Yeongsangang (silty loam) reclaimed tidal land. Electrical conductivity (EC) had a wide range from 0.0 to 34.3 dS ·m -1 during the experimental period. The average soil EC was 6.4 and 3.4 dS ·m -1 at Saemangeum and Yeongsangang reclaimed tidal land, respectively. Soluble sodium concentration had great variations and it was the most important single factor for temporal variations of soil EC regardless of soil textural properties. Calcium concentration was negatively correlated with soil EC and soluble sodium. Soil exchangeable sodium percentage (ESP) was estimated as a function of soil sodium adsorption ratio (SAR) and a linear regression model (ESP = 6.075 (SAR) + 0.677 for Saemangeum and ESP = 3.925 (SAR) + 0.421 for Yeongsangang reclaimed tidal soil) was suggested for predicting soil ESP from soil SAR. The characteristics of reclaimed tidal lands had different shares of saline and sodic properties during the experimental period. Saemangeum reclaimed tidal soil was highly characterized by sodium, but the effect of sodium on Yeongsangang soil was less pronounced. Our results indicate that persistent monitoring and modeling on soil salinity at reclaimed tidal soil is fundamental and the results can provide some useful information for deciding management plans for diverse utilization or to reduce salt damage for stable crop production at reclaimed tidal land.
Reclaimed tidal lands that locate mainly in west and south coastal areas of Korean peninsula are approximately 350,000 ha, which occupy about 21% of arable lands for crop production [
It is projected that salt damages in reclaimed tidal land is likely to increase with future climate change scenarios such as the rise in sea level and temperature that will subsequently increase evaporation rate and salt accumulation in root zone. It is well reported that salinity level in agricultural soils depends on the variations of many factors such as soil texture, plant growth, quality of irrigation water, hydraulic conductivity, and irrigation system in place [
The dynamic characteristics of soil salts depend on environmental factors such as nature of soils, the amount and type of soluble salts, and local hydrological conditions [
Soil salinity is highly variable by local climate, management practices, and environmental conditions. Reclaimed tidal lands showed the various levels of soil salinity regardless of its establishment time [
Reclaimed tidal lands are salt affected soils that parent material is fluvio-marine deposit soil. Based on soil texture, reclaimed tidal land in Korea can be classified as two categorized soils; 1) sandy loam and 2) silty loam [
The experimental sites have a temperate climate regions with the annual mean temperatures were 12.6˚C and 13.4˚C at Saemangeum and Yeongsangang reclaimed tidal land, respectively. The average long-term annual precipitation was 1250 mm at Saemangeum and 1325 mm at Yeongsangang reclaimed land, on which, about 50% falls between June and August. Under high soil salinity condition bare patches are observed devoid of any vegetation. Some salt tolerant grass species grown in experimental sites were manually removed by hands.
Three sampling sites were selected at each reclaimed tidal land and three cores of soil samples were taken by a hand spiral auger from surface (0 - 20 cm) and sub-surface (20 - 40 cm) layer weekly from April to November, 2013. The part of collected soil samples were used for mass water content by oven drying at 110˚C and the rest of samples were air-dried, passed through a 2-mm sieve, and then used for the chemical analysis. Soil pH and electrical conductivity (EC) was determined with pH electrode (Beckman PH1560, USA) and conductivity meter (Orion 162A, USA) from 1:5 soil/water suspension. Soil EC of a saturation paste extract was estimated from the EC using 1:5 soil/water suspension and an estimate of soil texture. Organic matter content was measured by Tyurin method (NIAST, 2000). Cation exchange capacity (CEC) was measured by 1N-NH4OAc at pH 7.0. Particle size distribution was conducted by using ASTM 152H hydrometer after dispersion with 5% sodium hexametaphosphate. Soluble and exchangeable cations were sequentially extracted with distilled water and 1N-NH4OAc (adjusted pH 7.0) and quantified by inductively coupled plasma-optical emission spectrometer (Varion Vista-MPX, Australia). Sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) are given as:
Na+, Ca2+, Mg2+ = exchangeable Na+, Ca2+, and Mg2+, respectively, in mmol∙kg−1;
CEC = cation exchangeable capacity, in mmol∙kg−1.
Based on soil EC and ESP values, study soils were classified into four groups: 1) soils with EC ≥ 4 dS∙m−1 and ESP < 15% are designated as saline, 2) soils with EC < 4 dS∙m−1 and ESP ≥ 15% are designated as sodic, 3) soils with EC ≥ 4 dS∙m−1 and ESP ≥ 15% are designated as saline-sodic, and 4) non-salt affected soils [
The data was statistically analyzed using analysis of variance (ANOVA) with the JMP statistical program (SAS institute ver. 5.0, USA). Means between treatments were compared by least significant difference and Tukey- Kramer HSD at 95% level when the F-test was statistically significant.
Soil Depth (cm) | pH (1:5) | EC (dS∙m−1) | OM (g∙kg−1) | Av.P2O5 (dS∙m−1) | Particle Size Distribution (%) | CEC (cmol∙kg−1) | |||
---|---|---|---|---|---|---|---|---|---|
Sand | Silt | Clay | Texture | ||||||
-------------------------------------------- Saemangeum -------------------------------------------- | |||||||||
0 - 20 | 7.9 | 2.4 | 2.5 | 70 | 66 | 33 | 2 | SL† | 5.8 |
20 - 40 | 7.7 | 3.3 | 2.0 | 32 | 59 | 39 | 2 | SL | 6.2 |
------------------------------------------- Yeongsangang ------------------------------------------- | |||||||||
0 - 20 | 8.5 | 2.7 | 11.6 | 142 | 27 | 60 | 13 | SiL | 15.0 |
20 - 40 | 8.7 | 5.8 | 8.1 | 40 | 21 | 65 | 14 | SiL | 15.4 |
†SL, sandy loam; SiL, silty loam.
During the experimental period, electrical conductivity (EC) had widely ranged from 0.1 to 34.3 dS∙m−1 at Sae- mangeum and from 0.0 to 8.8 dS∙m−1 at Yeongsangang reclaimed tidal land (
Soil EC values were significantly influenced by the interaction between sampling site and depth at Saeman- geum (
MWC† (%) | pH (1:5) | EC (dS∙m−1) | Soluble cations (cmol∙kg−1) | SAR | ESP (%) | |||
---|---|---|---|---|---|---|---|---|
Ca | Mg | Na | ||||||
------------------------------------------------------------- Saemangeum ------------------------------------------------------------- | ||||||||
Minimum | 8.5 (18.6) | 6.1 (6.5) | 0.1 (0.1) | 0.03 (0.05) | 0.10 (0.18) | 0.10 (0.15) | 0.6 (1.3) | 4.4 (9.0) |
Maximum | 36.3 (38.5) | 9.4 (9.3) | 34.3 (31.9) | 1.06 (0.74) | 4.27 (3.89) | 27.59 (19.26) | 9.3 (7.5) | 61.5 (42.8) |
Mean | 23.3 (25.1) | 7.8 (7.9) | 6.4 (6.1) | 0.16 (0.17) | 0.98 (0.95) | 5.61 (4.66) | 3.5 (3.8) | 21.5 (24.1) |
S.D. | 5.0 (2.5) | 0.5 (0.5) | 8.8 (7.1) | 0.15 (0.13) | 0.93 (0.57) | 7.70 (4.92) | 2.8 (1.3) | 14.3 (8.1) |
------------------------------------------------------------- Yeongsangang ------------------------------------------------------------ | ||||||||
Minimum | 9.7 (7.0) | 7.3 (7.1) | 0.0 (0.1) | 0.05 (0.08) | 0.21 (0.16) | 0.16 (0.27) | 0.2 (1.3) | 0.6 (4.4) |
Maximum | 48.0 (45.2) | 9.1 (9.1) | 8.8 (10.4) | 0.73 (0.88) | 5.47 (5.98) | 16.89 (17.64) | 4.7 (6.4) | 20.1 (26.5) |
Mean | 23.1 (26.7) | 8.1 (8.1) | 3.4 (4.9) | 0.40 (0.31) | 1.76 (1.36) | 3.02 (4.53) | 2.2 (3.5) | 9.3 (14.0) |
S.D. | 6.4 (7.1) | 0.4 (0.5) | 0.4 (0.5) | 0.13 (0.13) | 1.08 (1.23) | 1.74 (2.17) | 0.7 (1.1) | 3.4 (4.8) |
Values in parenthesis are values from sub-surface layer (20 - 40 cm). †MWC, mass water content; SAR, sodium adsorption ratio; ESP, exchangeable sodium percentage.
Location | Depth (cm) | MWC† (%) | pH (1:5) | EC (dS∙m−1) | Soluble (cmol∙kg−1) | SAR | ESP (%) | |
---|---|---|---|---|---|---|---|---|
Ca | Na | |||||||
Site 1 | 0 - 20 | 22.3 | 7.6 | 1.0 | 0.09 | 0.33 | 1.1 | 7.0 |
20 - 40 | 24.0 | 8.1 | 1.1 | 0.10 | 0.55 | 2.5 | 15.5 | |
Site 2 | 0 - 20 | 23.1 | 7.9 | 1.5 | 0.09 | 1.39 | 3.3 | 19.2 |
20 - 40 | 25.3 | 7.7 | 4.0 | 0.12 | 3.27 | 3.9 | 24.7 | |
Site 3 | 0 - 20 | 24.5 | 7.8 | 15.7 | 0.30 | 14.11 | 6.0 | 38.1 |
20 - 40 | 26.2 | 8.0 | 12.8 | 0.28 | 10.16 | 5.0 | 32.0 | |
p-value | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | |
LSD0.05 | 1.2 | 0.1 | 1.7 | 0.04 | 1.24 | 0.4 | 2.1 | |
Site 1 | 23.2 | 7.9 | 1.0 | 0.10 | 0.44 | 1.8 | 11.3 | |
Site 2 | 24.2 | 7.8 | 2.7 | 0.11 | 2.33 | 3.6 | 21.9 | |
Site 3 | 25.3 | 7.9 | 14.3 | 0.29 | 12.63 | 5.5 | 35.1 | |
p-value | <0.0001 | 0.0666 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | |
LSD0.05 | 0.9 | NS | 1.2 | 0.03 | 0.96 | 0.3 | 1.7 | |
0 - 20 | 23.3 | 7.8 | 6.1 | 0.16 | 5.61 | 3.5 | 21.5 | |
20 - 40 | 25.1 | 7.9 | 6.4 | 0.17 | 4.66 | 3.8 | 24.1 | |
p-value | <0.0001 | 0.0012 | 0.668 | 0.5962 | 0.1857 | 0.0715 | 0.0441 | |
LSD0.05 | 0.7 | 0.1 | NS | NS | NS | NS | 2.5 |
†MWC, mass water content; SAR, sodium adsorption ratio; ESP, exchangeable sodium percentage.
Location | Depth (cm) | MWC† (%) | pH (1:5) | EC (dS∙m−1) | Soluble (cmol∙kg−1) | SAR | ESP (%) | |
---|---|---|---|---|---|---|---|---|
Ca | Na | |||||||
Site 1 | 0 - 20 | 28.0 | 8.0 | 2.9 | 0.39 | 2.57 | 2.6 | 11.2 |
20 - 40 | 33.6 | 8.1 | 4.6 | 0.35 | 4.01 | 4.1 | 17.1 | |
Site 2 | 0 - 20 | 20.6 | 8.3 | 3.8 | 0.39 | 3.08 | 2.2 | 9.1 |
20 - 40 | 25.4 | 8.3 | 5.6 | 0.25 | 4.93 | 3.0 | 14.3 | |
Site 3 | 0 - 20 | 20.6 | 7.9 | 3.3 | 0.41 | 3.42 | 1.9 | 7.5 |
20 - 40 | 21.1 | 8.0 | 4.6 | 0.33 | 4.65 | 2.8 | 10.6 | |
p-value | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | |
LSD0.05 | 1.5 | 0.1 | 0.5 | 0.05 | 0.8 | 0.3 | 1.3 | |
Site 1 | 30.8 | 8.0 | 3.8 | 0.37 | 3.29 | 3.3 | 14.2 | |
Site 2 | 23.0 | 8.3 | 4.7 | 0.32 | 4.00 | 2.9 | 11.7 | |
Site 3 | 20.9 | 7.9 | 4.0 | 0.37 | 4.04 | 2.3 | 9.1 | |
p-value | <0.0001 | <0.0001 | <0.0001 | 0.0072 | 0.0197 | <0.0001 | <0.0001 | |
LSD0.05 | 1.2 | 0.1 | 0.4 | 0.04 | 0.59 | 0.3 | 1.1 | |
0 - 20 | 23.1 | 8.1 | 3.4 | 0.40 | 3.02 | 2.2 | 9.3 | |
20 - 40 | 26.7 | 8.1 | 4.9 | 0.31 | 4.53 | 3.5 | 14.0 | |
p-value | <0.0001 | 0.1577 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | |
LSD0.05 | 1.2 | NS | 0.3 | 0.03 | 0.46 | 0.2 | 0.9 |
†MWC, mass water content; SAR, sodium adsorption ratio; ESP, exchangeable sodium percentage.
The mean SAR and ESP values showed an identical distribution pattern to the mean EC values at Yeongsan- gang reclaimed tidal land (
Electrical conductivity is influenced by physical and chemical properties of soil including soluble salts, soil water content, bulk density, temperature, and organic matter content [
The data of this study showed that soil EC and ESP values were highly fluctuated during the experimental pe- riod, which resulted in different shares of saline and sodic properties of experimental soils (
Sol. | Sol. | Sol. | Sol. | Exch. | Exch. | Exch. | Exch. Na | SAR | ESP | ∑sol. | ∑Exch. | |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Ca | K | Mg | Na | Ca | K | Mg | ||||||
EC | 0.715 | 0.649 | 0.791 | 0.937 | −0.674 | 0.581 | 0.540 | 0.879 | 0.819 | 0.879 | 0.939 | 0.862 |
Sol. Ca | 0.540 | 0.529 | 0.768 | −0.640 | 0.705 | 0.056 | 0.953 | 0.977 | 0.953 | 0.757 | 0.694 | |
Sol. K | 0.809 | 0.686 | −0.442 | 0.532 | 0.390 | 0.609 | 0.570 | 0.609 | 0.733 | 0.631 | ||
Sol. Mg | 0.795 | −0.492 | 0.403 | 0.537 | 0.656 | 0.584 | 0.656 | 0.844 | 0.714 | |||
Sol. Na | −0.660 | 0.606 | 0.484 | 0.862 | 0.816 | 0.862 | 0.996 | 0.826 | ||||
Exch. Ca | −0.383 | −0.342 | −0.662 | −0.687 | −0.662 | −0.653 | −0.445 | |||||
Exch. K | 0.170 | 0.732 | 0.723 | 0.732 | 0.599 | 0.695 | ||||||
Exch. Mg | 0.286 | 0.139 | 0.286 | 0.501 | 0.674 | |||||||
Exch. Na | 0.980 | 0.985 | 0.857 | 0.851 | ||||||||
SAR | 0.980 | 0.806 | 0.747 | |||||||||
ESP | 0.857 | 0.851 | ||||||||||
∑Sol. | 0.832 |
∑sol. and ∑Exch. denote summation of soluble and exchangeable cations (Ca + K + Mg + Na) concentration, respectively.
Location | Depth (cm) | Normal† | Saline | Sodic | Saline-Sodic |
---|---|---|---|---|---|
------------------------------ % ------------------------------ | |||||
Saemangeum | 0 - 20 | 33.3 | 0.0 | 32.1 | 34.6 |
20 - 40 | 11.3 | 0.0 | 48.4 | 40.3 | |
Yeongsangang | 0 - 20 | 63.9 | 31.0 | 3.2 | 1.9 |
20 - 40 | 13.9 | 44.3 | 2.5 | 39.2 |
†Normal (EC < 4 dS∙m−1, ESP < 15%), Saline (EC ≥ 4 dS∙m−1, ESP < 15%), Sodic (EC < 4 dS∙m−1, ESP ≥ 15%), Saline-sodic (EC ≥ 4 dS∙m−1, ESP ≥ 15%).
Saemangeum soils were usually associated with high amounts of Na salt. These results were probably due to the characteristics of Saemangeum soil that has high contents of soluble Na, low values of cation exchange capacity and clay content. Contrary to Saemangeum soil, the characteristics of sodic or saline-sodic soils were occasio- nally found in the surface layer at Yeongsangang reclaimed tidal land. The percentage of non-salt affected cha- racteristics at Yeongsangang soil was much greater (63.9% vs. 13.9%) at the surface layer compared to the sub- surface layer. The percentage of normal soils at sub-surface layer was decreased and showed the predominant forms of saline and saline-sodic characteristics at sub-surface layer. The soil with higher levels of Na restricts water-holding capacity, prevent flocculation of soil particles and prevent water penetration [
The results of this study showed that there was great correlation between soil EC and soluble sodium content of reclaimed tidal soils regardless of soil texture. Soil ESP can be estimated from soil SAR due to the good linear regressions between soil ESP and SAR at both Saemangeum and Yeongsangang reclaimed tidal soils. Saeman- geum and Yeongsangang soils had different characteristics of saline and/or sodic soils during the growing sea- son. Saemangeum soils were associated with high amounts of sodium, but the effect of sodium on Yeongsan- gang soil was less pronounced. The data of this study indicated that any future management practice or land use plan at Saemangeum and Yeongsangang reclaimed tidal lands should be considered characteristics of soil salin- ity.
This study was carried out with the support of “Cooperative Research Program for Agriculture Science & Technology Development (Project No. PJ010258)” Rural Development Administration, Republic of Korea.