gypsum treatment, even though the 200 g m
−2 slag treatment had the same Ca input rate. This finding indicates that
the steelmaking slag dissolves more slowly than gypsum. On
the other hand, there were no differences in Na concentrations among the four treatments. The increase in the Na
concentration in the soil solution from 12 June to 3 July is
considered to be due to the progression of ferrous iron formation under submerged conditions and ion exchange
between ferrous iron in solution and Na ions at the soil
exchange sites. These results indicate that the desalinated
soil supplies a large amount of Na to rice plants and that the
application of slag and gypsum can increase plant-available
Ca in desalinated soils.
Relative to the control treatment, the slag treatments with
application rates of 200 and 400 g m
−2 increased brown rice
yields by 10% and 21%, respectively, and the latter significantly (Fig. 6.30). Gypsum treatment had little effect on the
rice yield, despite having a greater effect on increasing the
Ca and K contents and decreasing the Na content of rice
straw than did the 200 g m
−2 slag treatment (Figs. 6.31–
6.33). This result suggests that hydrogen sulfide was generated by the reduction of sulfate derived from gypsum and
inhibited rice root elongation and/or nutrient uptake and
reduced rice yield. The application of slag or gypsum
increased the Ca and K concentrations in rice straw by 9–
20% and 9–16%, respectively, relative to the control
(Figs. 6.31, 6.33), but decreased the Na concentrations by
11–16% (Fig. 6.32). The slag treatments significantly enriched the silicate contents of rice straw at maturity
(Fig. 6.34). These findings suggest that Ca-containing
Fig. 6.28 Temporal pattern of
calcium concentration in the soil
solution. Source Figure provided
by Toyoaki Ito, Hisashi
Nasukawa, Toru Uno, Ryousuke
Tajima, and Masanori Saito
Fig. 6.29 Temporal pattern of
sodium concentration in the soil
solution. Source Figure provided
by Toyoaki Ito, Hisashi
Nasukawa, Toru Uno, Ryousuke
Tajima, and Masanori Saito
6 Tohoku Region
223
−2 slag treatment had the same Ca input rate. This finding indicates that
the steelmaking slag dissolves more slowly than gypsum. On
the other hand, there were no differences in Na concentrations among the four treatments. The increase in the Na
concentration in the soil solution from 12 June to 3 July is
considered to be due to the progression of ferrous iron formation under submerged conditions and ion exchange
between ferrous iron in solution and Na ions at the soil
exchange sites. These results indicate that the desalinated
soil supplies a large amount of Na to rice plants and that the
application of slag and gypsum can increase plant-available
Ca in desalinated soils.
Relative to the control treatment, the slag treatments with
application rates of 200 and 400 g m
−2 increased brown rice
yields by 10% and 21%, respectively, and the latter significantly (Fig. 6.30). Gypsum treatment had little effect on the
rice yield, despite having a greater effect on increasing the
Ca and K contents and decreasing the Na content of rice
straw than did the 200 g m
−2 slag treatment (Figs. 6.31–
6.33). This result suggests that hydrogen sulfide was generated by the reduction of sulfate derived from gypsum and
inhibited rice root elongation and/or nutrient uptake and
reduced rice yield. The application of slag or gypsum
increased the Ca and K concentrations in rice straw by 9–
20% and 9–16%, respectively, relative to the control
(Figs. 6.31, 6.33), but decreased the Na concentrations by
11–16% (Fig. 6.32). The slag treatments significantly enriched the silicate contents of rice straw at maturity
(Fig. 6.34). These findings suggest that Ca-containing
Fig. 6.28 Temporal pattern of
calcium concentration in the soil
solution. Source Figure provided
by Toyoaki Ito, Hisashi
Nasukawa, Toru Uno, Ryousuke
Tajima, and Masanori Saito
Fig. 6.29 Temporal pattern of
sodium concentration in the soil
solution. Source Figure provided
by Toyoaki Ito, Hisashi
Nasukawa, Toru Uno, Ryousuke
Tajima, and Masanori Saito
6 Tohoku Region
223