ABSTRACT
Blending flue gas desulfurization (FGD) gypsum with surface sodic soil is a universally recognized method for the rapid amelioration of sodic soils; however, little information is available on whether other application methods (band application) will reclaim sodic soil. Three FGD gypsum application methods (single-band, dual-band and blend applications) and a control treatment (non-FGD gypsum) were carried out using sodic soil in soil bins to investigate the effects of the application method on the wetting front, major cations in the leachate during the process of water infiltration and soluble and exchangeable cations in the soil profile after infiltration. The results showed that the wetting fronts in the band treatments were denser in the horizontal direction than in the vertical direction, but the blend and control treatments only had vertical migration. The main channel of the stream in the band treatment was concentrated below the application site of FGD gypsum. The orders of desalting capacity were blend treatment, dual-band treatment and single-band treatment for the same volume of outlet water. There was no water outflow in the control treatment even after 115 days of leaching. The dual-band treatment significantly decreased the soil sodicity of the 0-40 cm soil profile, while the single-band treatment only effectively reclaimed (horizontally) half of the soil. In the blend treatment, the exchangeable sodium percentages were 21.3 % and 34.7 % at depths of 30-35 cm and 35-40 cm, respectively, and were close to zero at a depth of 0-30 cm. Compared with blend treatment, band application could be a better way to reclaim sodic soil with FGD gypsum due to its advantages of long-term and efficient amelioration with low consumption.
Subject(s)
Soil Pollutants , Soil , Calcium Sulfate , Rivers , WaterABSTRACT
Soil rotational tillage is an effective measure to overcome the problems caused by long-term of a single tillage, but the effect of the interval time of rotational tillage practices is not very well understood. Therefore, we conducted a 3-year field study in a wheat-maize cropping system to evaluate the effects of rotary tillage (RT) in rotation with plowing tillage (PT) on soil properties in northern China. Four practices were designed as follows: 3 years of RT to a depth of 10-15 cm (3RT), 3 years of PT to a depth of 30-35 cm (3PT), 1 year of PT followed by 2 years of RT (PT+2RT), and 2 years of PT followed by 1 year of RT (2PT+RT). Within 20 cm of the surface soil, the 3RT treatment significantly increased the soil quality index (SQI) by 6.0%, 8.8% and 13.1%, respectively, relative to the PT+2RT, 2PT+RT and 3PT treatments. The improvement was closely related to the significant increase in the soil organic carbon (SOC) and available nutrients concentrations in the 0-20 cm depths and the improvement of soil invertase, urease, alkaline phosphatase and catalase activities in the topsoil (0-10 cm). However, the opposite effects were observed in the subsoil (20-40 cm). Compared with the 3RT treatment, the 3PT, 2PT+RT and PT+2RT treatments decreased soil bulk density, and significantly enhanced enzyme activities, resulting in an increase in SQI of 32.6%, 24.4% and 0.7%, respectively, especially in the 3PT and 2PT+RT treatments, the difference was significant. When averaged across to all soil depths, the SQI under the 3RT and 2PT+RT treatments was much higher than that under the other treatments. The yields of wheat and maize under the 2PT+RT treatment were 15.0% and 14.3% higher than those under the 3RT treatment, respectively. The 2PT+RT treatment was the most effective tillage practice. These results suggest that RT in rotation with PT could improve soil quality in the soil profile whilst enhancing crop yield after continuous RT, and the benefits were enhanced with an interval time of one year. Therefore, the 2PT+RT treatment could act as an effective method for both soil quality and crop yield improvement in a wheat-maize cropping system under straw incorporation conditions.