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Not AvailableVertisols have the capacity to swell and shrink, inducing cracks and distinctive soil structure throughout the soil profile. The formation of these specific features is caused by a heavy texture, a dominance of swelling clay and marked changes in moisture content. In India they occur in various agro-ecological regions such as humid tropical (HT), sub-humid moist (SHM), sub-humid dry (SHD), semi-arid moist (SAM), semi-arid dry (SAD) and arid dry (AD) climatic environments and thus indicates an array of soils in a climosequence. In this study benchmark Vertisols, Panjari and Kheri are from sub-humid (moist) region, Teligi and Akola soils are from semi-arid (dry) and Nimone is from arid agro-ecological region. All the Vertisols are characterized by dark colour in surface soil, angular to sub-angular blocky structure, clayey texture, and slight to strong effervescence from upper to lower horizon of the soil profiles. These soils have high bulk density and high water retention capacity. The particle size distribution indicates all the soils are clayey with less amount of sand. In addition, they have deep wide-opened desiccation cracks at the surface which extend deep into the profiles and the depth of cracks increase with increase in aridity. The slickensides are found beginning at a shallower depth in arid climate, whereas they are observed at lower depths in wetter climates. Soils of all climates are dominated by Ca2+ ion in their exchange complex throughout the depth. However, in the sub-humid climate Mg2+ ions tends to dominate in the lower horizon. The semi-arid dry (Akola) soils have high Na+ ions in soil solution. This facilitated the translocation of Na-clay in the soil profile and is responsible for the increase in pH. Chemically the studied soils are slightly alkaline to alkaline in nature and poor in organic matter. The CEC varied from 40.8 to 50.18 cmol (p+) kh-1 in Panjari series profile which is highest followed by Teligi series profile. The calcium carbonate (CaCO3) shows gradual increase with depth in all the soil profiles, though it is preferentially accumulated in the sub-surface horizons of lower rainfall region soils. In climosequence the soils of the sub-humid region are generally Typic Haplusterts, soils of semi-arid region are Typic/Sodic/Calcic Haplusterts and soils of arid region are Sodic/ Calcic/ Aridic Haplusterts. The available potassium content (1 N NH4OAc extractable) of these soils is very high and available nitrogen is low. The potassium content in sub-humid moist (kheri) soil is high in surface horizon followed by semi-arid dry (Akola) soil. The ratio of exchangeable to non-exchangeable K varied from about 1:4 to 1:7. The variation is mainly due to mixing of different parent materials during the process of their formation.Not Availabl

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Not AvailableVertisols have the capacity to swell and shrink, inducing cracks and distinctive soil structure throughout the soil profile. The formation of these specific features is caused by a heavy texture, a dominance of swelling clay and marked changes in moisture content. in this study, benchmark Vertisols of Panjari and Kheri sub-humid (moist) region, Teligi and Akola soils semi-arid dry and Nimone arid agro-ecological region. All the Vertisols are characterized by dark colour in surface, angular to sub-angular blocky structure, clayey texture, and slight to strongly effervescent from upper to lower horizon of the soil profiles. These soils have high bulk density and water retention capacity. In addition, they have deep wide-opened desiccation cracks at the surface which extend deep into the profiles and the depth of cracks increase with increase in aridity. The slickensides are found beginning at a shallower depth in arid climate, whereas they are observed at lower depths in wetter climates. Soils of all climates are dominated by Cap' ion in their exchange complex throughout the depth. However, in the sub-humid climate me ions tends to dominate in the lower horizon. The semi-arid dry (Akola) soils have high Na` ions in soil solution. This facilitated the translocation of Na-clay in the soil profile and is responsible for the increase in pH. The soils are slightly alkaline to alkaline and poor in organic matter. The CEC varied from 40.8 to 50.18 cmol (rf) kg'' in Panjari soils which is highest followed by Teligi soils. The calcium carbonate (CaCO3) shows gradual increase with depth in all the soil profiles, though it is preferentially accumulated in the sub-surface horizons of lower rainfall region soils. In climo-sequence the soils of the sub-humid region are generally Typic Haplusterts, soils of semi-arid region are Typic/Sodic/Calcic Haplusterts and soils of arid region are Sodic/ Calcic/ Aridic Haplusterts. The available potassium content (1 NNH4OAc extractable) of these soils is very high and available nitrogen is low. The potassium content in sub-humid moist (Uteri) soil is high in surface horizon followed by semi-arid dry (Akola) soil. The ratio of exchangeable to non-exchangeable K varied from about 1:4 to 1:7. The variation is mainly due to mixing of different parent materials during the process of their formation.Not Availabl

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Not AvailableStudies to evaluate the release threshold level of potassium in Vertisols (shrink-swell soils) in different agro-ecological regions of India and how that may help in K fertility interpretations are rare. Thus the objectives of this study were (i) to evaluate the K status of Vertisols through release threshold levels and (ii) to relate the findings with soil K release and fertilizer management. Three established soil series samples were collected from Vertisols of different agro-ecological regions of India. Release threshold level (RTL) was assessed after equilibrating soil with 0.01M CaCl2 solution having series of soil: solution ratio, after which the remaining amount of exchangeable K was extracted with 1N NH4OAc (pH 7). Total amount of K extracted (KT = K desorbed in CaCl2 solution plus K extracted with 1 N NH4OAc) remained more or less constant with decreasing K-level up to a certain value ( say threshold value) below which KT increased sharply indicating K release from non-labile form. The threshold value in terms of K concentrations (Release Threshold Concentration) of Panjari, Nagpur, Maharashtra (TypicHaplusterts, Sub-humid dry), Teligi, Bellary, Karnataka (SodicHaplusterts, Semi-arid dry) and Kheri, Jabalpur, Madhya Pradesh (TypicHaplusterts, Sub-humid moist) soils were 0.044 – 0.049, 0.034 – 0.062 and 0.043 – 0.11 m M, respectively. The high release threshold K levels in terms of concentration and activity ratio (AR) were observed in soils of Teligi and Kheri series as compared to soils of Panjari series due to high content of trioctahedral mica in the former two soils. The relationships between clay minerals, release threshold level, exchangeable potassium and non-exchangeable potassium determined by 1 N HNO3 and sodium tetra-phenylborate (NaBPh4) have been discussed.Not Availabl

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Not AvailableStudies to evaluate the release threshold level of potassium in Vertisols (shrink-swell soils) in different agro-ecological regions of India and how that may help in K fertility interpretations are rare. Thus the objectives of this study were (i) to evaluate the K status of Vertisols through release threshold levels and (ii) to relate the findings with soil K release and fertilizer management. Three established soil series samples were collected from Vertisols of different agro-ecological regions of India. Release threshold level (RTL) was assessed after equilibrating soil with 0.01 M CaCl2 solution having series of soil: solution ratio, after which the remaining amount of exchangeable K was extracted with 1 N NH4OAc (pH 7). Total amount of K extracted (KT = K desorbed in CaCl2 solution plus K extracted with 1 N NH4OAc) remained more or less constant with decreasing K-level up to a certain value (say threshold value) below which KT increased sharply indicating K release from non-labile form. The threshold value in terms of K concentrations (Release Threshold Concentration) of Panjari, Nagpur, Maharashtra (Typic Haplusterts, Sub-humid dry), Teligi, Bellary, Karnataka (Sodic Haplusterts, Semi-arid dry) and Kheri, Jabalpur, Madhya Pradesh (Typic Haplusterts, Sub-humid moist) soils were 0.044–0.049, 0.034–0.062 and 0.043–0.11 mm, respectively. The high release threshold K levels in terms of concentration and activity ratio (AR) were observed in soils of Teligi and Kheri series as compared to soils of Panjari series due to high content of trioctahedral mica in the former two soils. The relationships between clay minerals, release threshold level, exchangeable potassium and non-exchangeable potassium determined by 1 N HNO3 and sodium tetra-phenyl borate (NaBPh4) have been discussed.Not Availabl

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Not AvailableThis article critically reviews the information regarding potassium (K) status of Indian soils based on research conducted since 1929. The patterns and lacunae regarding potassium consumption in India are also mentioned. The role of minerals in potassium availability vis-à-vis forms of potassium is discussed and elucidated with suitable clay mineralogical evi- dences. The article also highlights concepts of potassium availability to plants in Indian shrink-swell soils. Authors have pointed out the inefficacy of the universal method used for assessing plant-available K (1N NH4OAc) in Indian shrink-swell soil, as observed from extensive K response studies. The current practicesof assessing only plant available K arenot adequate to detect native changes in soil potassium. This paradoxical situation necessitates revision and revalidation of the existing potassium fertilizer rec- ommendations, which are being adopted since four decades. A holistic research envisaging soil test crop response and mineralogical studies will help in revising potassium evaluation methods in India,leading to judicious fertilizer application by the farmers.Not Availabl

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Not AvailableVertisols have the capacity to shrink andswell, inducing cracks and distinctive soil structure throughout the soil profile. In India they occur in various agro-ecological regions such as humid tropical (HT), sub-humid moist (SHM), sub-humid dry (SHD), semi-arid moist (SAM), semi-arid dry (SAD) and arid dry (AD) climatic environments and thus indicates an array of soils in a climosequence. In this study benchmark Vertisols, Panjari is from sub-humid (dry), Kheriis from sub-humid (moist) region, Teligi and Akola soils are from semi-arid (dry) and Nimone is from arid agro-ecological region. All the Vertisols in general are characterized by dark colour, angular to sub-angular blocky structure, clayin texture and calcareous. These soils have high bulk density and high water retention capacity. These soils have deep wide-opened desiccation cracks at the surface which extend deep into the profiles and the depth of cracks increases with aridity. Soils of all climates are dominated by Ca2+ ion in their exchange complex throughout the depth. However, in the sub-humid climate Mg2+ ions tends to dominate in the lower horizon. Whereas the semi-arid dry (Akola) soils have high Na+ ions in their exchange complex. The soils are slightly alkaline to strongly alkaline in nature and poor in organic matter. The CEC varied from 59.3 to 68.2cmol (p+) kg-1 in soil of Panjari series which is highest followed by Teligi series profile. The calcium carbonate (CaCO3) shows gradual increase with depth in all the soil profiles, though it is preferentially accumulated in the sub-surface horizons of lower rainfall region soils.In climosequence the soils of the sub-humid region are generally TypicHaplusterts, soils of semi-arid region are Typic/Sodic/Calcic Haplusterts and soils of arid region are Sodic/ Calcic/ AridicHaplusterts. The present study demonstrates how the soil properties of Vertisols in a different climate may help in inferring the change in climate in a geologic period.Not Availabl