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Potassium Status of Shrink-Swell Soils of India vis-à-vis their Mineralogical Composition

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Title Potassium Status of Shrink-Swell Soils of India vis-à-vis their Mineralogical Composition
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Creator Bhattacharyya, T., Pal, D.K., Chandran, P., Ray, S.K. and Wani, S.P.
 
Subject Potassium Status, Shrink-Swell, Soils, India, Mineralogical
 
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The shrink-swell soils commonly known as black soils (Vertisols and their intergrades) represent a wide area named as black soil region (BSR) of India covering a total area of 76.6 mh . These soils are potentially huge crop production zones in the country. These are extensively spread in the states of Chattisgarh, Madhya Pradesh, Gujarat, Rajasthan, Maharashtra, Andhra Pradesh, Tamil Nadu and Karnataka. Vertisols and their intergrades also occur in many other states including West Bengal, Odisa, Bihar, Punjab, Haryana, Uttar Pradesh and Jammu and Kashmir.
Micas have been reported to be the most important minerals to supply K to plants. The other minerals are K-feldspars. Unlike soils of the Indo-Gangetic Plains (IGP) the Vertisols and their intergrades in the BSR are not micaceous. This is because alluvium derived from the Deccan basalt to form black soils do not contain mica. Little amount of mica concentrated in silt and coarse clay fractions indicate their parental legacy as erosional and depositional episodes during the post Plio-Pleistocene period.
Research on muscovites and biotites indicates little or no alteration of these minerals. Retention of elementary layers of mica favours the release of K even in low amount. Role of mica minerals in terms of their nature, content and stage of weathering should be the key to understand K management in soils. Many workers have used the X-ray intensity of peak heights of (001) and (002) basal reflections of mica for characterizing as well as quantifying micas. This is based on the observation that 0.5 nm reflection is stronger in muscovite when compared to biotite micas. Since the (001) and (002) intensities ratio of trioctahedral mica is directly proportional to increased K concentration, many workers tried to quantify biotite mica in soils which can be utilized as an index of K-reserve in soils. The contents of biotite in shrink-swell soils in various size fractions through Ba-K batch type exchange was estimated (Nimkar, 2004). The cumulative amount of K released at the end of final extraction by different size fractions was considered as released amount mainly from biotite (Fig. 1). The amount of biotite in clay, silt and sand fractions of representative Vertisols of central India ranged from 1.0 to 1.6, 0.2 to 0.3 and 0.2 to 0.4 mg/100g mica, respectively. It constitutes 7 to 19, 2 to 3 and 2 to 5% of the total mica in those size fractions, respectively. In less than 2mm fine earth fraction biotite content rarely exceeds 1% which constitute 6-8% of total micas. Biotite content was also measured using peak height ratio (002/001) values in selected benchmark soils using the formula: biotite = (0.685 – Peak height ratio)/0.719. With the advent of modern software, the X-ray diffractograms offer a greater scope for developing a user-friendly model to estimate content of biotite in a mixture using various other parameters generated by softwares while scanning samples. Besides, georeferencing soil K datasets should be the other important step to estimate the K reserve in the black soils for periodic monitoring of changes in K status.

An attempt was earlier made to estimate the available K reserves in the BSR through the identified benchmark (BM) spots. Nearly 241 BM soils of the BSR were chosen from the soil database of the NBSS&LUP, Nagpur and from other published literatures. The size of the available K reserve was estimated using ammonium acetate extractable K, bulk density, areal extent of each soil series in different soil depths. Six bioclimatic classes are identified in BSR (arid: A, semi-arid dry: SAd, semi-arid moist: SAm, subhumid dry: SHd, subhumid moist: SHm and humid: H) of which SAm and SHd cover more than 70% area of the BSR. The study showed that SAM, SAD and SHD stored more than 80% of total available K reserve in the BSR. On the basis of AESRs, BSR was subdivided into five zones, such as northern, central, western, eastern and southern. The western zone occupies larger area than the other four zones. The data showed that the K reserve is maximum in northern and central zones in the BSR (36 Tg: 1 Tg = 1012g). The study also showed that humid bioclimatic class (MAR >1500 mm) stores less K reserve than the arid (MAR
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Date 2020-06-30T14:02:42Z
2020-06-30T14:02:42Z
2015-08-07
 
Type Presentation
 
Identifier Bhattacharyya, T., Pal, D.K., Chandran, P., Ray, S.K. and Wani, S.P. (2015) Potassium Status of Shrink-Swell Soils of India vis-à-vis their Mineralogical Composition. Paper presented at the Nineteenth Annual Convention and National Conference on “Application of Clay Science in Agriculture, Environment and Industry”, Clay Minerals Society of India, New Delhi, 7-8 August, 2015, Kolkata, pp.8.
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http://krishi.icar.gov.in/jspui/handle/123456789/37718
 
Language English
 
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