Effects of applying flue gas desulfurized gypsum on improvement and carbon sequestration in saline-sodic soils
Objective Global saline-alkali land covers extensive areas,with China alone having approximately 99 million hectares of such land.This issue is exacerbated by climate change and improper agricultural practices,posing a primary constraint on agricul-tural development in arid regions.Gypsum is recognized as an economical and environmentally friendly chemical amendment for saline-alkali soils.This study investigates the impact of desulfurized gypsum on the physicochemical properties of soil within the 0～40 cm depth range in desert saline-alkali areas of Xinjiang,aiming to elucidate its role in soil improvement and carbon sequestration.Furthermore,this research aims to reveal the quantitative relationship between the application rate of desulfurized gypsum and soil organic and inorganic carbon content and reserves,as well as the influence of various environmental factors on soil improvement processes.These findings will provide a scientific basis for the amelioration and carbon sequestration of saline-alkali soils in arid regions,thereby mitigating the adverse effects of soil salinization on agricultural productivity.Methods The study was conducted in the downstream area of the Tarim River,situated at the northeast edge of the Taklimakan Desert.The experimental design involved subdividing a 10 m×10 m plot into 30 smaller plots measuring 100 cm×100 cm each.Soil drilling was conducted at seven time points(1,2,3,5,7,21,and 42 d)post-treatment to obtain layered soil samples at depths of 0～20 cm and 20～40 cm.A range of soil parameters,including pH,electrical conductivity(σ),organic carbon con-tent(wo),inorganic carbon content(wi),soil bulk density,and soil water content(ws),were analyzed.Results and Discussion The study investigated the effects of different application rates of desulfurized gypsum(0,10,20,30,40,and 50 t/hm2)on soil improvement and carbon sequestration in the 0～40 cm soil layer.Results revealed a significant reduc-tion in soil pH within the 0～20 cm layer following desulfurized gypsum application,accompanied by increased soil salinity com-pared to the control treatment.Additionally,soil organic carbon storage peaked at an application rate of 40 t/hm2,exhibiting a 0.029 kg/m2 increase over the control.Compared to the control,soil inorganic carbon storage increased by 0.211 kg/m2 and 0.182 kg/m2 with application rates of 10 and 40 t/hm2 of desulfurized gypsum,respectively,while the remaining treatments showed lower inorganic carbon storage than the control.The impact of desulfurized gypsum on soil carbon sequestration was most pronounced within 0～7 days after application,with the greatest effect observed at an application rate of 40 t/hm2.Furthermore,correlation analysis indicated that changes in soil carbon storage were significantly associated with soil pH,soil salinity,precipi-tation,and evapotranspiration.Conclusion After the addition of desulfurized gypsum,the pH of the amended soil layer(0～20 cm)significantly decreased,exhibiting an inverse relationship with soil pH changes.Conversely,soil salinity increased with higher desulfurized gypsum application rates,particularly evident in the 0～20 cm layer,whereas the impact on the 20～40 cm layer was minimal.Within the 0～20 cm layer,treatment with 40 t/hm2 of desulfurized gypsum resulted in higher organic carbon and inorganic carbon content compared to other treatments.Carbon content decreased with increasing soil depth.Over time,desulfurized gypsum initially promoted inorganic carbon sequestration,but later stages of treatment showed an inhibitory effect on soil carbon sequestration.Furthermore,the study revealed that changes in soil carbon density were influenced by various factors,with significant correla-tions observed between soil pH,soil salinity,precipitation,evapotranspiration,and carbon storage.From the perspective of the improvement effect and carbon sequestration of saline-sodic soils,an application rate of 40 t/hm2 of flue gas desulfurized gypsum can significantly reduce soil pH and has a significant carbon sequestration effect.
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