| In recent years, a growing number of acidic soil improvers proved that people paid more and more attention to the problems caused by soil acidification. The steel slag was selected as acidic soil improver to study the improvement and safety of steel slag applied continuously in acidic soil in different rotation system. The main results are as follows: 1. Effects of steel slag on wheat-rice rotation in 2 yearsSteel slag Application could significantly increase wheat yield compared with control treatment(CT), but continuous application did not increase rice yield. Compared with CT at the time, the yield of first wheat season was increased by 215.81% ~ 504.65% and the yield of thrid wheat season was increased by 22.69% ~ 37.78%, the yield of fourth rice season was decreased by 4.96% ~ 19.28%. Application of steel slag could improve the aboveground biomass of wheat in mature period. Compared with CT at the time, the aboveground biomass was increased by 238.41% ~ 325.00% in first wheat season and it was increased by 17.76% ~ 40.24% in third wheat season after steel slag applied. Application of steel slag reduced the aboveground biomass of rice in mature period. Compared with CT at the time, the aboveground biomass was decreased by 2.29% ~ 22.24% in second rice season and it decreased by 5.22% ~ 24.22% in fourth rice season after steel slag applied. Compared with CT in rice season, the rice tiller number was declined after steel slag applied.Application of steel slag significantly increased the soil p H in wheat-rice-wheat-rice rotation. Compared with the CT of first wheat season, the soil p H was increased by 0.17 ~ 1.00 after steel slag was applied. Compared with the CT of second rice season, the soil p H was increased by 0.36 ~ 2.21 after steel slag was applied second time. Compared with the CT of thrid wheat season, the soil p H was increased by 0.56 ~ 2.68 after steel slag was applied third time. Compared with the CT of fourth rice season, the soil p H was increased by 0.80 ~ 2.41 after steel slag was applied fourth time. The soil organic content was reduced after third application of steel slag. Application of Steel slag reduced wheat soil alkaline hydrolysis nitrogen(N), but little effect on alkaline hydrolysis N in rice soil. Soil available phosphorus(P) was increased significantly when the amount of application red 3 g/kg in different periods. Application of steel slag decreased soil available potassium(K). The content of Soil exchangeable ca lcium, exchangeable magnesium and available silicon were increased with the increase of steel slag application. 2. Effects of steel slag on rape-maize-rape rotationSteel slag Application could significantly increase the rape yield compared with control treatment(CT). Compared with CT at the time, the rapeseed was increased by 10.34% ~ 357.47% in first rape season, the rapeseed was increased by 55.62% ~ 90.73% in third rape season. Application of steel slag could improve the aboveground biomass of rape and maize in mature period. Compared with CT at the time, the aboveground biomass of rape was increased by 54.83% ~ 171.80% in first rape season and it was increased by 18.54% ~ 42.34% in third rape season after steel slag applied and the aboveground biomass of maize was increased by 16.14% ~ 22.43% in second maize season.Application of steel slag significantly increased the soil p H in rape-maize-rape rotation. Compared with the CT of first rape season, the soil p H was increased by 0.10 ~ 1.12 after steel slag was applied first time. Compared with the CT of second maize season, the soil p H was increased by 0.17 ~ 2.02 after steel slag was applied second time. Compared with the CT of thrid rape season, the soil p H was increased by 0.31 ~ 2.68 after steel slag was applied third time. The application of steel slag didn’t show the effect on the soil organic matter in rape-maize-rape rotation. The soil alkaline hydrolysis nitrogen was decreased with the increase of steel slag application, but it was decreased significantly compared with CT when the amount of application steel slag was more than 1 g/kg in different period. Soil available phosphorus(P) was increased significantly compared with CT when the amount of application red 3 g/kg in different periods. Application of steel slag decreased soil available potassium(K). The content of Soil exchangeable calcium, exchangeable magnesium and available silicon were increased with the increase of steel slag application.3. Effects of steel slag continuous application on safety of soil and foodAfter rounds of steel slag application, the total content of chromium(Cr), cadmium(Cd) and arsenic(As) in soil d id not increase significantly compared with CT and they did not exceed the Soil Environment Quality Standards Ⅱ.The content of Cr was less than 0.7 mg/kg and the content of Cd and As was not detected in the grains. The content of Cr was decreased in grain after steel slag applied. The content of Cr, Cd and As did not accumulate in grains and their contents were within the limits of standard of contaminants limits in foods. The application of steel slag could decrease the content of iron(Fe) manganese(Mn) in stem and leaf of rice. The content of Mn in grains was decreased when the amount of application was more than 2 g/kg. |
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