Seok-In Yun

Distribution of Heavy Metals in Soils of Shihwa Tidal Freshwater Marshes

Shihwa tidal freshwater marsh was constructed recently to treat pollutants entering Shihwa lake. In this study, we examined the spatial and temporal patterns of heavy metal accumulation in soils of Shihwa marsh and sought correlations between several soil variables (pH, electrical conductivity, organic matter, and acid ammonium oxalate-extractable Fe and Al contents) and the heavy metal concentration of soils. Surface soil samples (0∼20 cm) were collected in June 2000, November 2000, and July 2001, and were analyzed for heavy metals (Zn, Cd, Pb, Cu, Cr, As, and Hg) and soil chemical properties. The neutral pH and water-saturated conditions of Shihwa marsh appeared to favor immobilization of heavy metal through adsorption onto soils. The concentrations of heavy metal (especially Zn, Cu, and Cr) in soils of Shihwa marsh increased along the sampling occasions, suggesting that soils of Shihwa marsh serve as a sink of heavy metal. Among the sub-marshes, metal concentrations were highest in Banweol high marshes and lowest in Samhwa marshes. The temporal and spatial variations in the heavy metal concentrations of soils were correlated positively with organic matter and oxalate extractable Fe and Al contents, but negatively with electrical conductivity. These results suggest that organic matter and hydrous oxide of Fe/Al may playa key role in removing heavy metals in soils of Shihwa marsh, and that heavy metal removing capacity would increase with desalinization. However, the removal patterns of heavy metal by reeds warrant further studies to evaluate the total removal capacity of heavy metals by Shihwa marsh.

Yield Response of Chinese Cabbage to Compost,Gypsum, and Phosphate Treatments under the Saline-sodic Soil Conditions of Reclaimed Tidal Land

Salt stress in crops in reclaimed tidal lands can be reduced by applying soil amendments. To evaluate the effects of compost, gypsum, and phosphate on the growth of Chinese cabbage in saline-sodic soil conditions, we conducted a pot experiment in 2013 and 2014. The treatments consisted of a standard fertilizer application of a mix of compost and N-P-K fertilizer (S) and standard fertilizer applications with additional compost (S + C), gypsum (S + G), phosphate (S+P), and gypsum and phosphate (S + GP). The mean dry matter yield of cabbage in 2014 was three times as great as that in 2013, although soil EC (Electrical conductivity) in 2014 was not decreased. However, the mean ratio of sodium ion in soil solution (SAR1:5) significantly decreased from 17.3 ± 1.1 in 2013 to 11.2 ± 2.7 in 2014. Application of gypsum had the greatest positive impact on the growth of Chinese cabbage. The S + G treatment increased dry matter yield by 7.0 (48.2) and 7.9 g/plant (16.6%) in 2013 and 2014, respectively, compared to the S treatment. Applying gypsum increased soil EC, but decreased SAR1:5 by 14 and 38% in 2013 and 2014, respectively. The application of compost and phosphate had a small effect on the growth of Chinese cabbage. These results suggest that applying gypsum in reclaimed tidal lands can reduce the sodicity of the soil and improve crop growth.

Partitioning of N-uptake from 1-year of fertigation with 15N-urea in pot-lysimeter-grown M.9-grafted apple trees after 3 years of fertigation with unlabelled urea at three rates of N

Summary The total amounts of N derived from 15N-urea in the organs of 18 newly-bearing “maiden” apple trees and in the soil were determined after 1-year of fertigation with 15N-urea by drip irrigation, scheduled at a soil matric potential of –50 kPa. Prior to this treatment, the 18 “maiden” apple trees had been fertigated with three concentrations of N for 3 years: 17 mg N l–1 (low), 34 mg N l–1 (medium), or 67 mg N l–1 (high), and the same rates of 15N were chosen for treatment comparisons over the following 1 year. The trees were fertiligated with an aqueous stock solution of 15N-labelled urea (1.5 atom % 15N), KH2PO4, and KCl by drip irrigation. The phosphorus (P) and potassium (K) concentrations were constant, and set at 17 mg l–1 and 34 mg l–1, respectively. The total irrigation volume applied per tree was 363 l for the low, 430 l for the medium, and 216 l for the high N treatment.The corresponding supplies of N per tree were 6.17, 14.62, and 14.47 g, respectively. The total amounts of urea-N absorbed per tree were 1.90 g for the low-N, 3.73 g for the medium-N, and 3.21 g for the high-N treatments, with the percentage of N recovery (30.8%, 25.5%, and 22.1%) decreasing with increasing N rate, while the N retained in the soil was 2.92 g (47.3%), 7.40 g (50.6%), and 8.35 g (55.7%), respectively. Fertiliser N contributed more to whole-tree N uptake at increasing rates of N than N uptake from the soil. The total recovery of 15N from each tree-soil system was 78.1% at the low, 76.1% at the medium, and 79.8% at the high N level, with an average of approx. 22.0% of N unaccounted-for. The total amounts of P and K taken up were 2.42 g tree–1 and 14.49 g tree–1 for the low-N, 2.47 g tree–1 and 15.33 g tree–1 for the medium-N, and 1.31 g tree–1 and 8.04 g tree–1 for the high-N treatments, respectively. Our results showed that an N concentration of 34 mg l–1 (medium) resulted in more productive and profitable trees, bearing more fruit of higher quality than the other two N treatments. This concentration of N also improved the development of new leaves and flowers during the early stages of growth in the following Spring.

Effects of Compost and Gypsum on Soil Water Movement and Retention of a Reclaimed Tidal Land

Compost and gypsum can be used to ameliorate soil physicochemical properties in reclaimed tidal lands as an organic and inorganic amendment, respectively. To evaluate effects of compost and gypsum on soil water movement and retention as a soil physical property, we measured the soil’s saturated hydraulic conductivity and field capacity after treating the soil collected in a reclaimed tidal land with compost and gypsum. Saturated hydraulic conductivity of soil increased when compost was applied at the conventional application rate of 30 Mg ha -1 . However, the further application of compost insignificantly (P > 0.05) increased saturated hydraulic conductivity. On the other hand, additional gypsum application significantly increased soil saturated hydraulic conductivity while it decreased soil field capacity, implying the possible effect of gypsum on flocculating soil colloidal particles. The results in this study suggested that compost and gypsum can be used to improve hydrological properties of reclaimed tidal lands through increasing soil water retention and movement, respectively.

Changes of Saturated Hydraulic Conductivity of Bed-soils Mixed with Organic and Inorganic Materials

Bed-soils can be used to help plants to overcome unfavorable conditions of soils, especially hydraulic properties of soils. This study was conducted to evaluate the effect of organic and inorganic raw materials on saturated hydraulic conductivity (K s ) of bed-soils. Perlite and bottom ash, which are inorganic materials, increased more Ks of bed-soils than coco peat, an organic material. However, vermiculite, an inorganic material, increased less than coco peat. Saturated hydraulic conductivity of bed-soil mixed with fine vermiculite (0.14 ± 0.02 m h -1 ) was much lower than one containing coarse vermiculite (0.85 ± 0.21 m h -1 ). Such effect was more apparent when pressure was added on bed-soils containing fine vermiculite (0.07 ± 0.01 m h -1 ), probably reflecting the decrease in pore size with the expansion of vermiculite wetted. Compacting decreased more Ks in the bed-soils containing coco peat or vermiculite than other mixtures. Those results suggest that perlite and bottom ash in bed-soils play an important role in improving saturated hydraulic conductivity but vermiculite in bed-soils may suppress the improvement of saturated hydraulic conductivity with the decrease of its size and with the increase of compacting pressure.

Effects of Dolomite and Oyster Shell on Nitrogen Processes in an Acidic Mine Soil Applied with Livestock Manure Compost

Mine soils are usually unfavorable for plant growth due to their acidic condition and low contents of organic matter and nutrients. To investigate the effect of organic material and lime on nitrogen processes in an acidic metal mine soil, we conducted an incubation experiment with treating livestock manure compost, dolomite, and oyster shell and measured soil pH, dehydrogenase activity, and concentration of soil inorganic N (NH₄ + and NO₃ - ). Compost increased not nly soil inorganic N concentration, but also soil pH from 4.4 to 4.8 and dehydrogenase activity from 2.4 to 3.9 μg TPF g -1 day -1 . Applying lime with compost significantly (P -1 day -1 ) compared with applying only compost. Here, the variation in dehydrogenase activity was significantly (P<0.05) correlated with that in soil pH. Soil inorganic N decreased with time by 14 days after treatment (DAT) due to N immobilization, but increased with time after 14 DAT. At 28 DAT, soil inorganic N was significantly (P<0.05) higher in the lime treatments than the only compost treatment. Especially the enhanced dehydrogenase activity in the lime treatments would increase soil inorganic N due to the favored mineralization of organic matter. Although compost and lime increased soil microbial biomass and enzyme activity, ammonia oxidation still proceeded slowly. We concluded that compost and lime in acidic mine soils could increase soil microbial activity and inorganic N concentration, but considerable ammonium could remain for a relatively long time.

Salt Removal in a Reclaimed Tidal Land Soil with Gypsum, Compost, and Phosphate Amendment

High salinity and sodicity of soils play a negative role in producing crops in reclaimed tidal lands. To evaluate the effects of soil ameliorants on salt removal in a highly saline and sodic soil of reclaimed tidal land, we conducted a column experiment with treating gypsum, compost, and phosphate at 0-2 cm depth and measured the salt concentration of leachate and soil. Electrical conductivity of leachate was 45-48 dS m -1 at 1 pore volume (PV) of water and decreased to less than 3 dS m -1 at 3 PV of water. Gypsum significantly decreased SAR (sodium adsorption ratio) of leachate below 3 at 3 PV of water and soil ESP (exchangeable sodium percentage) below 3% for the whole profile of soil column. Compost significantly decreased ESP of soil at 0-5 cm depth to 5% compared with the control (20%). However, compost affected little the composition of cations below a depth of 5 cm and in leachate compared with control treatment. It was concluded that gypsum was effective in ameliorating reclaimed tidal lands at and below a soil layer receiving gypsum while compost worked only at a soil layer where compost was treated.