Potassium（K） is known as one of the essential nutrients for the growth of plant species. The relationship between K and clay minerals can be used to understand the K cycling, and assess the plant uptake and potentia...Potassium（K） is known as one of the essential nutrients for the growth of plant species. The relationship between K and clay minerals can be used to understand the K cycling, and assess the plant uptake and potential of soil K fertility. This study was conducted to analyze the K forms（soluble, exchangeable, non-exchangeable and structural） and the relationship of K forms with clay minerals of calcareous soils in Kohgiluyeh and Boyer-Ahmad Province, Southwest Iran. The climate is hotter and drier in the west and south of the province than in the east and north of the province. A total of 54 pedons were dug in the study area and 32 representative pedons were selected. The studied pedons were mostly located on calcareous deposits. The soils in the study area can be classified into 5 orders including Entisols, Inceptisols, Mollisols, Alfisols and Vertisols. The main soil clay minerals in the west and south of the study area were illite, chlorite and palygorskite, whereas they were smectite, vermiculite and illite in the north and east of the province. Due to large amount of smectite and high content of organic carbon in soil surface, the exchangeable K in surface soils was higher than that in subsurface soils. It seems that organic matter plays a more important role than smectite mineral in retaining exchangeable K in the studied soils. Non-exchangeable K exhibited close relationships with clay content, illite, vermiculite and smectite. Although the amount of illite was the same in almost all pedons, amounts of structural and non-exchangeable K were higher in humid regions than in arid and semi-arid regions. This difference may be related to the poor reservoir of K~＋ minerals like palygorskite and chlorite together with illite in arid and semi-arid regions. In humid areas, illite was accompanied by vermiculite and smectite as the K~＋ reservoir. Moreover, the mean cumulative non-exchangeable K released by CaCl_2 was higher than that released by oxalic acid, which may be due to the high buffering capacity resulting from high carbonates in soils.展开更多
In addition to sequestering carbon in soil,biochars can also play a role in changing the potassium equilibration and dynamics of the soil.Nowadays,acidification of biochar is commonly used to improve its properties,wh...In addition to sequestering carbon in soil,biochars can also play a role in changing the potassium equilibration and dynamics of the soil.Nowadays,acidification of biochar is commonly used to improve its properties,which can impact the potassium content in the soil.Simultaneous application of acidified biochar and sodium bentonite can complicate this effect.In the present study,the effects of adding two types of biochars prepared from municipal waste and used coffee grounds and their acidified types,along with sodium bentonite at three levels(0.00%,1.00%,and 2.00%),on soil physical-chemical properties(pH,salinity,cation exchange capacity,concentration of soluble cations and their ratio,and sodium adsorption ratio)and the release of potassium from a calcareous soil were investigated.The results showed that the addition of coffee ground biochar increased the concentration of soluble potassium and decreased the ratio of calcium to potassium,while the acidified coffee ground biochar decreased the amount of soluble potassium and increased the ratio of calcium to potassium.Alkaline and acidified municipal waste biochars had no effect on soluble potassium and soluble cations ratio.Application of bentonite increased the amount of soluble calcium and sodium and the ratio of calcium to potassium.Addition of bentonite also increased the amount of exchangeable potassium and exchangeable sodium percentage,but use of different biochars reduced negative effect of bentonite.Use of bentonite also caused an increase in the exchangeable potassium and a decrease in the non-exchangeable potassium contents.Alkaline and acidified coffee ground biochars increased the amount of exchangeable,non-exchangeable,and total potassium,but this effect was greater by alkaline biochar.Application of municipal waste biochar did not affect the amount of exchangeable potassium but increased the amount of non-exchangeable and total potassium,with no significant difference observed between alkaline and acidified biochars.Potassium saturation percentage was not affected by bentonite,but coffee ground biochar increased its amount and municipal waste biochar had no effect on it.Acidified and alkaline coffee ground biochars were able to release more potassium from the soil(475 and 71 mg/kg,respectively),while alkaline municipal waste biochar did not affect it and acidified municipal waste biochar reduced it by 113 mg/kg.In general,it can be concluded that alkaline biochars in calcareous soils can improve potassium fertility by reduction of the ratio of calcium to potassium and increasing its various forms,while acidified biochars and bentonite may aggravate potassium deficiency in these soils.Considering the lack of significant change in the pH of calcareous soils with the use of different biochars,it is suggested to use alkaline biochars,which can improve the potassium status of the soil while reducing the costs associated with biochar modification.展开更多
文摘Potassium（K） is known as one of the essential nutrients for the growth of plant species. The relationship between K and clay minerals can be used to understand the K cycling, and assess the plant uptake and potential of soil K fertility. This study was conducted to analyze the K forms（soluble, exchangeable, non-exchangeable and structural） and the relationship of K forms with clay minerals of calcareous soils in Kohgiluyeh and Boyer-Ahmad Province, Southwest Iran. The climate is hotter and drier in the west and south of the province than in the east and north of the province. A total of 54 pedons were dug in the study area and 32 representative pedons were selected. The studied pedons were mostly located on calcareous deposits. The soils in the study area can be classified into 5 orders including Entisols, Inceptisols, Mollisols, Alfisols and Vertisols. The main soil clay minerals in the west and south of the study area were illite, chlorite and palygorskite, whereas they were smectite, vermiculite and illite in the north and east of the province. Due to large amount of smectite and high content of organic carbon in soil surface, the exchangeable K in surface soils was higher than that in subsurface soils. It seems that organic matter plays a more important role than smectite mineral in retaining exchangeable K in the studied soils. Non-exchangeable K exhibited close relationships with clay content, illite, vermiculite and smectite. Although the amount of illite was the same in almost all pedons, amounts of structural and non-exchangeable K were higher in humid regions than in arid and semi-arid regions. This difference may be related to the poor reservoir of K~＋ minerals like palygorskite and chlorite together with illite in arid and semi-arid regions. In humid areas, illite was accompanied by vermiculite and smectite as the K~＋ reservoir. Moreover, the mean cumulative non-exchangeable K released by CaCl_2 was higher than that released by oxalic acid, which may be due to the high buffering capacity resulting from high carbonates in soils.
文摘In addition to sequestering carbon in soil,biochars can also play a role in changing the potassium equilibration and dynamics of the soil.Nowadays,acidification of biochar is commonly used to improve its properties,which can impact the potassium content in the soil.Simultaneous application of acidified biochar and sodium bentonite can complicate this effect.In the present study,the effects of adding two types of biochars prepared from municipal waste and used coffee grounds and their acidified types,along with sodium bentonite at three levels(0.00%,1.00%,and 2.00%),on soil physical-chemical properties(pH,salinity,cation exchange capacity,concentration of soluble cations and their ratio,and sodium adsorption ratio)and the release of potassium from a calcareous soil were investigated.The results showed that the addition of coffee ground biochar increased the concentration of soluble potassium and decreased the ratio of calcium to potassium,while the acidified coffee ground biochar decreased the amount of soluble potassium and increased the ratio of calcium to potassium.Alkaline and acidified municipal waste biochars had no effect on soluble potassium and soluble cations ratio.Application of bentonite increased the amount of soluble calcium and sodium and the ratio of calcium to potassium.Addition of bentonite also increased the amount of exchangeable potassium and exchangeable sodium percentage,but use of different biochars reduced negative effect of bentonite.Use of bentonite also caused an increase in the exchangeable potassium and a decrease in the non-exchangeable potassium contents.Alkaline and acidified coffee ground biochars increased the amount of exchangeable,non-exchangeable,and total potassium,but this effect was greater by alkaline biochar.Application of municipal waste biochar did not affect the amount of exchangeable potassium but increased the amount of non-exchangeable and total potassium,with no significant difference observed between alkaline and acidified biochars.Potassium saturation percentage was not affected by bentonite,but coffee ground biochar increased its amount and municipal waste biochar had no effect on it.Acidified and alkaline coffee ground biochars were able to release more potassium from the soil(475 and 71 mg/kg,respectively),while alkaline municipal waste biochar did not affect it and acidified municipal waste biochar reduced it by 113 mg/kg.In general,it can be concluded that alkaline biochars in calcareous soils can improve potassium fertility by reduction of the ratio of calcium to potassium and increasing its various forms,while acidified biochars and bentonite may aggravate potassium deficiency in these soils.Considering the lack of significant change in the pH of calcareous soils with the use of different biochars,it is suggested to use alkaline biochars,which can improve the potassium status of the soil while reducing the costs associated with biochar modification.
