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ISSN : 2287-5824(Print)
ISSN : 2287-5832(Online)
Journal of The Korean Society of Grassland and Forage Science Vol.45 No.2 pp.128-139
DOI : https://doi.org/10.5333/KGFS.2025.45.2.128

Effects of Gypsum Application on Dry Matter Yield and Mineral Content of Alfalfa, and Soil Properties in Reclaimed Tidal Land

Ji Yung Kim1, Doohong Min1, Kyung Il Sung2, Jinglun Peng3, Sourajit Dey1, Myung Kyo Kim4, Rudra Baral5, Byong Wan Kim2*
1Department of Agronomy, Kansas State University, Manhattan, Kansas 66506, USA
2Department of Animal Life Science, Kangwon National University, Chuncheon 24341, South Korea
3College of Pastoral Agriculture Science and Technology, State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, Lanzhou University, Lanzhou 730020/730000, China
4School of Business, Hanyang University, Seoul 04763, South Korea
5University of Missouri Extension, Columbia, Missouri 65211, USA
* Corresponding author: Byong Wan Kim, Department of Animal Life Science, Kangwon National University, Chuncheon 24341, South Korea. Tel: +82-33-250-8625, E-mail: bwkim@kangwon.ac.kr
June 3, 2025 June 23, 2025 June 24, 2025

Abstract


The objective of this study was to assess the effects of gypsum application on dry matter yield (DMY), mineral content of alfalfa (Medicago sativa L.), and soil properties in reclaimed tidal land in South Korea. The experiment was conducted in Seokmun, located on the west coast of South Korea, which is reclaimed with approximately 70 cm depth of degraded island soil. Treatments consisted of a control with no gypsum application (G0), 2 ton ha-1 (G2), and 4 ton ha-1 (G4) of gypsum application. The first harvest was carried out when the alfalfa reached 10% flowering, and subsequent harvests were conducted at 35-day intervals. Over the three-year experimental periods (2019-2021), the total DMY of G2 treatment was significantly higher than those of G0 and G4 (p<0.05). Although both G2 and G4 gypsum application treatments lowered soil pH, the G4 treatment increased the electrical conductivity (EC) content of the soil. Additionally, gypsum application affected the mineral contents of alfalfa, resulting in reduced concentration of sodium (Na) and Magnesium (Mg). Therefore, this present study suggests that a gypsum application rate of 2 ton ha-1 is optimal for improving alfalfa dry matter yield and mineral balance, as well as enhancing soil chemical properties in reclaimed tidal land in South Korea.


Alfalfa , Gypsum , Reclaimed tidal land , Dry matter yield , Mineral content , Soil chemical property

초록

    Ⅰ. INTRODUCTION

    In South Korea, alfalfa (Medicago sativa L.), a high-quality forage with high protein content, is entirely reliant on imports for its supply (Rural Development Administration; RDA, 2021). Due to the increasing demand for livestock feed, there is a high demand for alfalfa production. However, in South Korea, it is challenging to cultivate alfalfa, a perennial legume, due to limited available land (Kim et al., 2023). As a result, there is a need for new land for the production of perennial forages.

    Kim et al. (2023) suggested the necessity of using reclaimed land to expand the cultivation of alfalfa in South Korea. The total area of reclaimed tidal land is 350,000 ha, accounting for about 21% of the South Korea’s agricultural land areas (Lee et al., 2013). The soil of the reclaimed tidal land has various physical and chemical properties (Lee, 2009). The topsoil of reclaimed tidal land in South Korea has a pH of 7.5 for alfalfa cultivation, but the salinity concentration was higher than that of field soil (RDA, 2017). In particular, the high exchangeable sodium (Na) content of reclaimed soil may result in poor drainage and physiological drought or toxicity (Rye et al., 2010).

    To cultivate alfalfa in reclaimed tidal land, it requires improvements in both physical and chemical soil properties due to the crop’s sensitivity to soil drainage (a physical property) and pH (a chemical property) (Undersander et al., 2011a). One major challenge of growing alfalfa is to mitigate soil salinity in reclaimed tidal land. To address this, soil drainage can be enhanced through soil dressing to improve the aggregated soil structure (Sohn et al., 2007). Continuous management is required as soil chemistry on reclaimed tidal land is constantly changing due to precipitation and fluctuations in ground water level of the soil (Lee, 2009). Gypsum application can help in managing these soil chemical fluctuations. Gypsum (CaSO4·2H2O) regulates the exchange of calcium (Ca) ions with Na ions in soil particles, lowering soil salinity and improving soil permeability (Son et al., 2016).

    Kim et al. (2021) reported that alfalfa can be cultivated in reclaimed tidal lands using gypsum to mitigate soil salinity. However, their study primarily evaluated the feasibility of alfalfa cultivation based on biomass production and forage quality using a gypsum application rate of 2 ton ha-1. Thus, further assessment is needed to understand how gypsum application affects other factors, such as the mineral content of the alfalfa. There is limited research on the optimal gypsum application rate for alfalfa cultivation in reclaimed tidal lands in South Korea, particularly regarding its impact on soil properties and plant nutrition. Gypsum application increases the concentration of exchangeable Ca in the soil, which can influence the uptake of other essential cations such as Na, magnesium (Mg), and potassium (K). These changes can alter the overall nutrient balance required for optimal alfalfa growth, as suggested by Kim et al. (2021).

    In particular, high soil salinity, especially elevated levels of exchangeable Na, increases soil osmotic pressure, severely restricting crop growth (Koo et al., 1998). During alfalfa cultivation, excessive Na⁺ in the soil can interfere with the uptake of key nutrients such as nitrogen (N), Ca, K, and Mg (Ryu et al., 2010), leading to deficiencies in essential elements, such as N and K (Bhattarai et al., 2020). When the Na concentration in the soil exceeds that within plant tissues, the resulting osmotic stress reduces water and nutrient absorption, ultimately causing plant wilting (Bhattarai et al., 2020).

    It is crucial to investigate how Na concentrations respond to different gypsum application rates in reclaimed tidal land soils. In particular, changes in alfalfa mineral content may cause risks to livestock health, such as grass tetany (Grunes and Welch, 1989), when alfalfa is used as forage.

    Therefore, this study was conducted to evaluate the effects of gypsum application on dry matter yield, mineral content of alfalfa, and soil chemical properties in reclaimed tidal land, following the research of Kim et al. (2021).

    Ⅱ. MATERIALS AND METHODS

    This study was carried out at 70 cm depth of the reclaimed tidal land of Seokmun in Songsan-myeon, Dangjin-si, Chungcheongnam-do (N36°58'12.00', E126°38'59.61'), South Korea. The reclaimed tidal land of Seokmun has poor drainage due to its low slope and high salinity (RDA, 2022). The soil used for soil dressing in this study was mined from an island area in 2018 and had not undergone salinity removal treatment. The soil texture at the experimental site was classified as sandy loam. The soil chemical properties were as follows, pH 8.6, available phosphorus (P₂O₅) 21.53 mg kg⁻¹, cation exchange capacity (CEC) 7.46 cmol kg⁻¹, and exchangeable cations such as Ca, K, Mg, and Na at 8.88, 0.10, 4.33, and 0.21 cmol kg⁻¹, respectively. The electrical conductivity (EC) was 0.47 dS m⁻¹ (Table 1). The pH in the present study was higher than that of the existing reclaimed tidal land, but the EC was lower than that of the sodic soil (Son et al., 2016). The alfalfa variety used in this research was common, and it was planted in rows on October 02, 2018, at a seeding rate of 20 kg ha-1.

    The experiment was fertilized with N, phosphorus (P), K, and boron (B) at a rate of 100, 300, 300, and 20 kg ha-1, respectively. The experimental site had N, P, K, and organic matter (OM) lower than the optimal standards for cultivating forage (RDA, 2019). In this research, fertilizers such as N, P, K, and B were applied in the year of sowing. N and B were not applied during production years (i.e., 2019, 2020, and 2021) as top dressing. P was applied right after the first and last harvests whereas K was applied after each harvest.

    Three different levels of gypsum (G) application were tested: No gypsum (control, G0), 2 ton ha-1 (G2) and 4 ton ha-1 (G4). The gypsum application rate was based on the recommendation of 2 - 3 ton ha-1 for rice cultivation in high salinity paddy fields (Hwang et al., 1990). The experiment was designed as a randomized complete block design with three replications. Each plot size was 1m x 2m resulting in a total area of 2 m2. Gypsum was applied in the seeding year according to the treatment rates, but not in the first production year. It was subsequently applied in the second and third production years at green-up in early spring.

    The first harvest of alfalfa was carried out at the early bloom stage (10% flowering), and 1st harvest after harvesting was performed at approximately 35-day intervals. Adjustments were made for each harvest based on weather conditions, particularly rainfall (Table 2). Additionally, the cutting interval between the 2nd and 3rd harvests in the second production year was shortened to 25 days. This earlier harvest adjustment was made due to the forecasted continuous rainfall resulted from monsoon season in South Korea.

    For insect and weed control, alfalfa weevil (Hyperapostica) infestation occurred, prompting an earlier harvest than the optimal harvest time for management purposes at the 1st harvest of the second production year. In the third production year, alfalfa weevil occurred and insecticides (Etofenprox) were applied on May 9, 2021. Weeds namely shepherd's purse (Capcella bursa-pastoris), dandelion (Taraxacum officinale), thistle (Cirium japonicum var. maackii), horseweed (Conyza canadensis), barnyard millet (Echinochlo utilis), and Cyperus iria (Cyperus iria L.) were identified during the study.

    The samples were dried in hot-air ovens at 65˚C for 72 hours to determine dry matter (DM) content and calculate DMY (kg ha-1). The alfalfa proportion was calculated as the ratio of the DMY weight of alfalfa to the total DMY of alfalfa and weeds in the plot. The first and second production year data were previously reported by Kim et al. (2021), and DMY of third prodcution year was collected using the same method from Kim et al. (2021).

    Dried alfalfa samples were ground in a 20 mesh mill (Fritsch, Germany) and stored in a shaded place until alfalfa mineral contents analysis. The mineral contents (i.e., Na, K, Ca, and Mg) of alfalfa were measured after the first and last harvests in each production year. The pretreatment for the analysis of mineral contents was performed by adding 10 ml of hydrochloric acid solution to ground samples. The samples were then allowed to stand for 24 hours before being filtered (MAFRA, 2019). The ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer; Agilent Technologies, Inc., USA, Model 5900) was used to analyze the mineral contents.

    For analysis of the soil physicochemical properties, soil samples were collected from each treatment at planting and after the first and last harvests in each production year. The soil measurements included soil texture, pH, OM, EC, exchangeable cation (Ca2+, Mg2+, K+, and Na+), CEC, exchangeable sodium percentage (ESP), and P2O5. The collected soil samples were air-dried in the shade, passed through a 2 mm sieve, and used for analysis. Soil texture was measured using a hygrometer. The pH and EC were measured using a solution of dried soil and distilled water at a 1:5 ratio for 30 minutes (RDA, 2010). The available phosphorus was analyzed using the Lancaster method and OM using the Tyurin method (RDA, 2010). The exchangeable cation was measured using the inductively coupled plasma (ICP) method by adding 50 ml of 1 M ammonium acetate (NH4OAc, pH 7.0) to a 5 g soil sample and shaking for 30 minutes (RDA, 2010). The CEC was analyzed by simplified measurement (RDA, 2010). The ESP was calculated to confirm the concentration of water-soluble salts (Jung and Ha, 2015), which can adversely affect the growth of crops. The ESP was calculated suing the formula:

    Among the climate data, the daily mean temperature was measured at hourly intervals by putting a data logger (DT-172, CEM) at the experimental site, and was calculated according to the standards of the Korea Meteorological Administration (KMA). Precipitation data was collected from the weather data service-Open MET data portal on KMA (data.kma.go.kr). The climate information used was recorded at Seosan Automated Synoptic Observing System (ASOS), which was the closest meteorological station to the experimental site.

    For statistical analysis, SPSS 24.0 (IBM corp., 2019) was used, and the mean comparison of DMY, mineral content, and soil chemical properties were tested by the least significant difference (LSD) method at the 95% the significance level at each production year and three-year total years.

    Ⅲ. RESULTS AND DISCUSSION

    1. Weather condition

    The monthly temperature during the experimental period (March to October) in the production years was higher than the 30-year average except for July in the second production year (Fig. 1). The average annual precipitation over the past 30 years was 1,253.9 mm. In the years leading up to 2019, 2020, and 2021, the recorded precipitation amounts were 915.0, 1,488.7, and 1,006.9 mm, respectively (Fig. 2). The precipitation during the alfalfa growth period in the first and third production years was lower than the 30-year average. Monthly precipitation was lower than the 30-year average, except for September and October in the first production year. In the third production year, the precipitation was higher in spring (March to May) and lower in summer (June to August) compared to the past 30-year average. On the other hand, the monthly precipitation in the second production year was higher than the 30-year average, especially from July to September, which resulted in low temperatures in July.

    2. Dry matter yield

    The three-year total DMY in 2019, 2020, and 2021 was 43,827, 50,596, and 42,912 kg ha-1, respectively. G2 had a significantly higher DMY than G0 and G4 (p<0.05; Fig. 3). Over the production years, the DMY of first production year (17,060, 21,107, and 17,831 kg ha-1 for G0, G2, and G4, respectively) was G2 had a significantly higher DMY than G0 and G4 (p<0.05; Table 3). The second production year (17,005, 17,223, and 16,150 kg ha-1 for G0, G2, and G4, respectively; Table 3) and third production year (9,762, 10,311, and 8,930 kg ha-1 for G0, G2, and G4, respectively; Table 3) were not significantly differed by treatment. This decrease in DMY across climate effects, especially precipitation, was due to huge fluctuations in the production years.

    In the present study, the DMY of alfalfa for all gypsum treatments in all production years exceeded the average annual DMY of 12,536 kg ha-1 (n=270) for domestic alfalfa as reported by Kim et al. (2023) except for the third production year. Among all the treatments, G2 had the highest DMY in this study. The production of alfalfa in reclaimed tidal land was significantly influenced by the soil pH and EC (Steve, 2007). As a method of lowering the soil pH and EC of the reclaimed tidal land, soil dressing, a physical or chemical treatment of gypsum can be used (Son et al., 2001;RDA, 2014;Son et al., 2016). In this study, gypsum was believed to increase the alfalfa DMY in the reclaimed tidal land to make optimum soil conditions for cultivating alfalfa.

    The DMY of cool-season grass generally tends to be higher in the second and third production years compared to the first production year after planting (Kim et al., 2001). However, this study showed that the DMY of alfalfa was lower in the second and third production years than in the first production year. This reason was the difference in precipitation by the production years. Since both the amount and seasonal distribution of precipitation are key factors influencing alfalfa's growth, regrowth, and yield (Takele and Kallenbach, 2001;Shewmaker et al., 2011;Baral et al., 2022). Ideally, alfalfa thrives with around 1,000 mm of annual precipitation (Kim et al., 1995;John, 1998), indicating optimal growth conditions in the first production year. The precipitation in the second production year was 1,488.7 mm, which exceeded the recommended rate and may have negatively impacted alfalfa growth, as it is sensitive to high soil moisture content. In the third production year, the precipitation until September was 1,006.9 mm, and in March and May, it was higher than the 30-year average (Fig. 2). Considering the precipitation and mean temperature, it initially seemed that the growing conditions for alfalfa up to the 1st harvest were favorable. However, in reality, alfalfa growth was hindered by the lasting effects of the higher-than-average precipitation in the second production year of the study as compared to a 30-year average. Consequently, the 1st harvest in the third production year was delayed until mid-June due to this growth depression.

    In this study, the highest alfalfa DMY occurred in 2 ton ha-1 of gypsum application. This result was similar to Kim et al. (2021). It is believed that this might have occurred due to improvements of the soil chemical properties in cultivating alfalfa in reclaimed tidal land.

    3. Soil properties

    During the three-year experimental period, the soil pH for treatments G0, G2, and G4 was measured at 8.26, 7.55, and 7.65, respectively. Notably, the soil pH in the G0 treatment was higher than in both G2 and G4 treatments (p<0.05; Fig. 4A). The application of gypsum appeared to lower the soil pH compared to the control. In the present study, soil pH before gypsum application was 8.60, which was higher than the optimum pH range of 6.3 to 7.5 (Steve, 2007;Undersander et al., 2011a;2011b). This might be attributed to the high salinity concentration as the soil used for the experiment was from an island and there was no separate decontamination treatment. Steve (2007) suggested that determining the suitability of a site for cultivating alfalfa should be based on the soil pH. In the first and third production years, the pH of G0 was undesirable, but in G2 and G4, it was marginal, suggesting that the gypsum application helped lower the soil pH. The soil pH drop in G2 and G4 treatments might be due to the acidification of the soil as the sulfur content in the soil increased across all the gypsum treatments. A similar tendency was reported by Ehsan et al. (2022). In the second production year, G2 was significantly lower than G0 and G4 (p<0.05), the soil pH indicated that G0 and G4 treatments were marginal, while a G2 treatment was ideal. In addition, the soil pH in G4 was significantly higher than that in G2 (p<0.05) and also higher compared to the values observed in other years. This increase is likely attributable to the significantly higher Na content in the G4 soil compared to G2 (p<0.05). Therefore, it appears that the soil pH decreased to a suitable level for alfalfa cultivation by applying gypsum to alfalfa grown in reclaimed tidal land. Additionally, it was found that higher precipitation than usual during the alfalfa growth period might have contributed to lowering the soil pH as precipitation influenced the leaching of the cations present in the soil (Mun et al., 1996).

    The soil EC during the three-year experimental periods for treatments G0, G2, and G4 were 0.76, 1.52, and 4.24 dS m-1, respectively, with G4 being significantly higher than G0 and G2 (p<0.05; Fig. 4B). An EC of 2.0 dS m-1 or less is within the normal range (Maas and Hoffman, 1977;Tanji, 2002) that did not affect DMY (Tanji, 2002). An EC over 3.4 dS m-1 starts to cause a 10% reduction in DMY and an EC of 6.8 dS m-1 or more results in a 50% reduction (Alforex seed, 2013). In terms of soil EC standards (Steve, 2007), in the first production year, G0 and G2 treatments were ideal for alfalfa cultivation but a G4 treatment was undesirable. In contrast, in the second production year, all gypsum treatments were suitable for alfalfa cultivation. In the third production year, G0 and G2 treatments remained ideal, but G4 was undesirable. The unsuitability of G4 in the first and third production years might be attributed to the significant increase in Ca due to the application of 4 tons of gypsum per hectare, leading to increased salinity and a subsequent decrease in DMY. The G0 and G2 did not exceed 2.0 dS m-1, whereas G4 reached 7.32 dS m-1, significantly higher than the other treatments, which affected DMY in first production year. The absence of differences in DMY between treatments in the second and third production years might be due to the suitable EC across treatments. Therefore, applying 2 ton ha-1 of gypsum in the reclaimed tidal land maintains optimal EC for DMY production of alfalfa.

    Throughout the experimental period, the levels of exchangeable Ca in the soil for treatments of G0, G2, and G4 were 9.16, 9.88, and 16.81 cmol kg-1, respectively. A G4 treatment had significantly higher levels of exchangeable Ca than G0 and G2 treatments (p<0.05; Fig. 4C). Additionally, the G4 consistently showed higher levels of exchangeable Ca than G0 and G2 treatments in every production year (p<0.05). Both soil EC and exchangeable Ca increased with increasing gypsum application rate.

    The exchangeable K in the soil for treatments of G0, G2, and G4 had significant differences among the treatments (p<0.05; Fig. 4D). A G4 treatment had higher levels of exchangeable K than G0 and G2 treatments as increased gypsum application rate treatment during all production years (p<0.05).

    Exchangeable Mg and Na, and ESP were not affected by gypsum application for three-year experimental periods (p>0.05; Fig. 4E-F). The exchangeable Mg content varied significantly throughout the experimental period. If the exchangeable Mg content was above 2.083 cmol kg-1 in the soil, alfalfa did not show deficiency. However, an exchangeable Mg appeared to be low in both G2 and G4 treatments in the third production year. Meanwhile, there was no difference in exchangeable Na in the first production year, but in the second production year, G4 treatment had significantly higher Na than other treatments (p<0.05; Fig. 4E). In the second year, the sodium content of G4 was significantly higher, which is thought to be due to the large fluctuations in the physical and chemical properties of reclaimed soil each year (Yang et al., 2008). In the third production year, both G0 and G2 treatments showed significantly higher levels of exchangeable Na than G4 treatment (p<0.05; Fig. 4F). The high exchangeable Na content reduced the biomass, forage quality, stand establishment, and leaf development of alfalfa (Al-Farsi et al., 2023). However, since the exchangeable Na content remained below 0.978 cmol kg-1, alfalfa cultivation was minimally affected by Na during this experimental period. The trend of ESP appeared similar to exchangeable Na content. ESP was no significant differences among treatments during the first and second production years. In the third production year, both G0 and G2 treatments showed significantly higher ESP than the G4 treatment (p<0.05; Fig. 4G). Throughout the experimental period, ESP did not exceed 7.0.

    The soil EC, Mg and Na contents showed significant variations across the production years (Fig. 4). The variability in soil chemical properties in reclaimed tidal land might be attributed to site and temporal difference, often caused by re-salinization of the surface soil. Re-salinization occurs due to increased capillary rise, driven by strong sunlight and low precipitation (Sohn et al., 2009). The level of re-salinization varies depending on the season, peaking in June (RDA, 2014). In addition, RDA (2022) reported that cultivating whole crop maize in reclaimed tidal land for more than 3 years has led to increase soil salinity due to re-salinization. Soil samples from the third production year were collected in June when there was low precipitation and high temperature, leading to re-salinization, which resulted in significant variations in soil chemical properties.

    In contrast, the first production year experienced lower precipitation than the third production year and re-salinization did not occur immediately after soil dressing. However, by the third production year, seawater containing high concentrations of salinity (Jung and Yoo, 2007) had affected the experimental site over time. Throughout the experimental period, the ESP remained below 7, which was the threshold for alfalfa cultivation recommended by Steve (2007). Therefore, the ESP levels did not negatively impact the DMY of alfalfa in any treatment.

    Considering the soil chemical properties, the greater gypsum application rate was 2 ton ha-1 due to the optimum range of soil pH and EC for cultivating alfalfa.

    4. Mineral contents in alfalfa

    Crops absorb mineral nutrients competitively based on their nutrient availability in the soil. In particular, the Na concentration increases the absorption of K, Ca, and Mg in alfalfa tissue (Al-Farsi et al., 2023;Li et al., 2010). Also, excessive exchangeable Na in sodic soils competes with exchangeable Ca and reduces the availability of other cations (Steve, 2007). The Na concentration over the experimental period was 0.07%, 0.05%, and 0.05% in the G0, G2, and G4 treatments, respectively. These results indicate that the Na concentration in the G0 treatment was significantly higher than in G2 and G4 (p<0.05). Also, The Na concentration was higher in G0 compared to G2 and G4 in the first and second production years (p<0.05; Fig. 5A). Meanwhile, the Na amount decreased with increasing gypsum application rate except in the third production year (p<0.05).

    In alfalfa, Ca has antagonistic effects with Na and Mg and synergistic effects with K (Ensiye et al., 2018). The Ca concentration in the G0, G2, and G4 treatments was 1.20, 1.18, and 1.30%, respectively, with no significant difference across the experimental period (p>0.05; Fig. 5B). Moreover, there was no significant difference each production year among the treatments (p>0.05). Gypsum treatment did not affect the Ca concentration in alfalfa. A similar result for Ca concentration was found by Chen et al. (2005) and Tirado-Corbalá et al. (2017).

    The K concentration in alfalfa, similar to Ca concentration, showed no significant difference among treatments of G0, G2, and G4, with concentrations of 2.53, 2.59, and 2.67%, respectively (p>0.05; Fig. 5C). There was no difference in production years by treatments (p>0.05), however, the K concentration tended to increase in all treatments for the production year. There was no significant difference in the concentration of Ca and K due to gypsum treatments across all experiment years (p>0.05). This study satisfied the K concentration level for alfalfa cultivation as the K concentration suitable for alfalfa cultivation ranges between 1.4% to 3.0%. In general, the high Na concentration in alfalfa caused a reduced K concentration through competition (Li et al., 2010). In this study, however, the exchangeable Na content did not appear to be high enough to cause salt stress.

    The Mg concentration was 0.32, 0.27, and 0.27% in treatments G0, G2, and G4, respectively during the experimental period. The treatment G0 showed a higher Mg concentration compared to G2 and G4 (p<0.05; Fig. 5D). However, there were no differences in the production years within each treatment (p>0.05). Tirado-Corbalá et al. (2017) reported a decrease in the Mg concentration caused by gypsum application, but this study did not observe this effect. For this reason, although their study was conducted over 12 years, the researchers did not observe differences in gypsum effects for 4 years. The Mg concentration tended to decrease over the production year. This trend has the potential to create diseases such as grass tetany in ruminants.

    The findings from a current study indicated that the exchangeable Ca and K levels in the soil decreased as the compositional year passed, but the Mg concentration of alfalfa tended to decrease continuously due to the increase in K concentration of alfalfa for production years and the exchangeable Na level in the soil in the third production year. Due to differences in concentration of K, Ca, and Mg, grass tetany in ruminants can occur by dividing K by the sum of Ca and Mg ratio values exceeding 2.2 (Grunes and Welch, 1989). It could appear in the ruminants if the alfalfa produced is fed in the third production year due to the ratio of Ca to Mg closer to 2.2 (in the range of 2.1 - 2.2).

    In this study, gypsum reduced the Na concentration of alfalfa in the reclaimed tidal land. Although both G2 and G4 treatments reduced the Na concentration of alfalfa, 2 ton of gypsum was recommended due to its low application rate of gypsum.

    Ⅳ. CONCLUSIONS

    This study aimed to assess the impact of gypsum application rate on the dry matter yield and the mineral content of alfalfa, as well as the soil properties from reclaimed tidal land for the potential expansion of alfalfa production in South Korea. The results showed that gypsum had a positive effect on alfalfa yield and mineral content. The soil chemical properties improved as gypsum was applied. Based on three-year study, it is recommended that the relatively ideal application rate of gypsum is 2 ton ha-1 to grow alfalfa in reclaimed tidal land in South Korea. However, this study had a limitation in that the soil chemical properties of the reclaimed land fluctuated during experimental periods. Therefore, it is thought that an evaluation should be conducted using data accumulated through long-term research.

    Ⅴ. ACKNOWLEDGEMENTS

    This study supported through the “Damage assessment in forages and development of cultivation technology for their damage reduction according to extreme weather (RDA-PJ014 99604)” through Rural Development Administration, Korea and the research grant of Kangwon National University in 2023.

    Figure

    KGFS-45-2-128_F1.gif

    Monthly mean temperature of 30-year average and the study years in Songsan-myeon, Dangjin-si, Chungcheongnam-do, South Korea.

    KGFS-45-2-128_F2.gif

    Monthly accumulated precipitation of 30-year average with first, second, and third production years in Suseok-dong, Seosan-si, Chungcheongnam-do, South Korea.

    KGFS-45-2-128_F3.gif

    Total dry matter yield of alfalfa during production years after gypsum application in reclaimed tidal land, G0 : Zero gypsum application, G2 : Applied gypsum of 2 ton ha-1, G4 : Applied gypsum of 4 ton ha-1, ab Means within the same bar with different superscripts differ (p<0.05).

    KGFS-45-2-128_F4.gif

    Change in soil properties: pH (A), electrical conductivity (B), Ca (C), K (D), Mg (E), Na (F), and exchangeable sodium percentage (G) across the experimental period, G0 : No applied Gypsum, G2 : Applied Gypsum of 2 ton ha-1, G4 : Applied Gypsum of 4 ton ha-1, abc Means within the same bar with different superscripts differ (p<0.05).; ns No significance different of each bar, * The data for the first and second production years were previously reported by Kim et al. (2021).

    KGFS-45-2-128_F5.gif

    Concentration of Na (A), Ca (B), K (B), and Mg (D) in alfalfa forage during experimental period, G0 : No applied Gypsum, G2 : Applied Gypsum of 2 ton ha-1, G4 : Applied Gypsum of 4 ton ha-1, ab Means within the same row with different superscripts differ (p<0.05).; ns No significance different of each row.

    Table

    Soil physical and chemical properties between pre- and post-reclaimed tidal land

    1) EC : Electrical Conductivity, 2) OM : Organic Matter, 3) CEC : Cation Exchange Capacity.

    Alfalfa harvest dates during the production years (2019 to 2021)

    Alfalfa dry matter yield during production years by gypsum application in reclaimed tidal land

    G0 : Zero gypsum application, G2 : Applied gypsum of 2 ton ha-1, G4 : Applied gypsum of 4 ton ha-1.
    ab Means within the column with different superscripts differ (p<0.05).; ns No significance different of column.
    * The data for the first and second production years were previously reported by Kim et al. (2021).

    Reference

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