Potassium status and clay mineralogical composition some sugarcane soils of North Karnataka

Transcription

1 Symposium no. 28 Paper no. 360 Presentation: poster Potassium status and clay mineralogical composition some sugarcane soils of North Karnataka HEBSUR Narayana S. and SATYANARAYANA T. University of Agricultural Sciences, Dharwad , India Abstract Ten surface soils belonging to orders viz., Vertisol, Inceptisol (mixed red and black) and Alfisol derived from diverse parent materials from major sugarcane growing areas of North Karnataka were considered to study the distribution of different forms of potassium and mineralogical composition of clay. The range in contents of various forms of potassium in different soils was 2.0 to mg kg -1 of water soluble K, to mg kg -1 of exchangeable K, 150 to 1250 mg kg -1 of non-exchangeable K,175 to 450 kg ha -1 of available K, 0.51 to 3.25% of lattice K and 0.58 to 3.3% of total potassium. The soils in general had contained medium to high available potassium with large total K reserve. The soil clays were dominantly smectitic in Vertisols and kaolinitic in Alfisol and Inceptisol. Inceptisol alone had recorded the presence of vermiculite (8.5%) and interestingly one of the Vertisols had contained almost equal amounts of kaolinite and montmorillonite. The potash bearing mineral mica was noticed in all the soil clays. Invariably, all Vertisols had contained about 10.0 percent kaolinite in their clay fractions. The higher available K status of the Inceptisol soil could be attributed to the presence of potash rich minerals. The continuous sugarcane crop has not much reduced the available K status of these soils. Keywords: sugarcane, North Karnataka, potassium status, potash bearing minerals, form of potassium Introduction Sugarcane is one of the major commercial crops grown extensively on a varieties of soils in Karnataka. It is a devourer of potassium, its need reaching 600 to 800 kg K 2 O per harvest. The information pertaining to status, distribution and mineralogy of potassium in soils of North Karnataka under sugarcane based cropping system is rather scant. Hence, an attempt is made to obtain adequate information on these aspects. Materials and Methods Ten surface soils (0-15 cm depth) belonging to orders viz., Vertisol, Inceptisol (mixed red and black) and Alfisol (red soil) derived from diverse parent materials were collected from major sugarcane growing areas of North Karnataka. The details of soils collected and some of their properities are presented in Table 1. The different forms of soil potassium were determined by adopting standard procedures. Clay separation and ion saturation of clays were carried out by following the procedure as outlined by Jackson (1976). After X-ray diffraction analysis, the semi-quantitative determination of minerals present in the clay samples was done according to the modified procedure as suggested by Ghosh and Datta (1974)

2 HEBSUR & SATYANARAYANA 17 th WCSS, August 2002, Thailand Table 1 Details of the soils selected for study Sample No. Location Parent material i* Gangavati Granitegneiss Soil classification Very fine, montmorillonitic, ii* Siruguppa Granite Very fine, montmorillonitic, iii** Kamalapur Granite Fine, loamy, mixed isohyperthermic, typic ustochrepts iv* Arabhavi Sand sotone Very fine, montmorillonitic, isohyperthermic, typic chromusterts v* Godageri Deccan trap Very fine, montmorillonitic, vi* Sankeshwar Deccan trap Very fine, montmorillonitic, vii* M.K.Hubli Deccan trap Very fine, montmorillonitic, isohyperthermic, typic chromusterts viii* Hunnur Deccan trap Fine, montmorillonitic, isohyperthermic, typic pellusterts ix* Mudhol Deccan trap Very fine, montmorillonitic, isohyperthermic, typic chromusterts x*** Bidar Granite Fine, mixed, isohyperthermic, typic paleustalfs *Vertisols **Inceptisols ***Alfisols ph EC (ds m -1 ) OC (g kg -1 ) CaCO3 Clay

3 HEBSUR & SATYANARAYANA 17 th WCSS, August 2002, Thailand Table 2 Contents of various forms of soil potassium and percent distribution of minerals in the clay fractions of soils. Sample No. Water soluble Exchangeable Different forms of soil potassium Percent distribution of minerals in the clay Non-exchangeable Available Lattice Total Smectite Chlorite Vermiculite Mica Kaolinite Intergrade l* * ll* Tr lll** lv* V* VI* TR Vll* Vlll* lx* X*** *Vertisols **Inceptisols ***Alfisols -Not identified 360-3

4 HEBSUR & SATYANARAYANA 17 th WCSS, August 2002, Thailand Table 2 (Cont.). Sample No. Location Different forms of soil potassium Percent distribution of minerals in the clay Water soluble Exchangeable Non-exchangle Available Lattice Total Smectite Chlorite Vermiculite Mica Kaolinite Intergrade l* * * ll* Tr lll** * lv* * V* * VI* * Vll* * Vlll* * lx* X*** * 360-4

5 HEBSUR & SATYANARAYANA 17 th WCSS, August 2002, Thailand Results and discussion The soils were alkaline (ph ranged from 7.4 to 9.0 ), non-saline (EC ranged from 0.13 to 0.90 ds m -1 ) and calcareous in nature (CaCO 3 > 2.5%). All the Vertisols are clay in texture, mixed red and black and red soils belonged to the textural class sandyloam. The semi-quantitative estimate revealed the presence of the highest amount of mica (42.0%) in Hunnur soil followed by Kamalapur mixed red and balck soil (22.2%). The potash bearing mineral mica was noticed in all soils but feldspar was not identified in any of the soil clays. The highest kaolinite (66.0%) was recorded Bidar red soil followed by mixed red and black soil (53.7%). Interestingly almost equal amounts of smectite (47%) and kaolinite (44%) were recorded in Arabhavi Soil Only red and black soil sample exhibited the presence of vermiculite (8.5%). Invariably, all Vertisols contain about 10 percent kaolinite in their clay fractions. The results pertaining to the forms of K in soils revealed that the Hunnur soil had the highest amount of water soluble, exchangeable and non-exchangeable K which also recorded greater amounts of lattice and total potassium. This could be attributed to the presence of higher amounts of mica-k bearing mineral which on weathering releases and contributes to various forms of soil potassium. Interestingly mixed red and black and red soils also showed higher exchangeable and non-exchangeable K status that way comparable with Vertisols. As reported by Patiram and Prasad (1991), the high K status in these soils is associated with the presence of comparable amounts of K rich micaceous and other 2:1 minerals as evident from the semi-quantitative clay mineralogical studies. Based on average available K content, all the Vertisols could be grouped under high category (>150 mg kg -1 ). Even the Kaolnite dominated soils (Kamalapur and Bidar) were also high in available potassium. Brar et al. (1986) also noticed upto 185 mg kg -1 available K in some kaolinite dominant soil series of southern India. The lower available K values in some of the Vertisols as compared to mixed red and black and red soils could be attributed to continuous mono-cropping of sugarcane in these soils. Nevertheless, when the soil parameters viz., exchangeable, available and total soil K are considered, the soils under study may not respond much to the application of potassium. The application of just the recommended dose of potash fertilizer to sugarcane as a maintenance dose is sufficient for these soils. Conclusions Despite the presence of greater amounts of kaolnite, mixed red and black and red soils had the K status that way comparable with Vertisols considered to be rich in potassium. Arabhavi Vertisol derived from sand stone had almost equal amounts of smectite and kaolnite. Based on parameters viz., exchangeable, available and total K, the soils under study may not respond much to the application of potassic fertilizer. Continuous mono-cropping of sugarcane has not decreased the availability of potassium in these soils. Acknowledgement The authors acknowledge with thanks the University of Agricultural Sciences, Dharwad for providing facilities during the course of the present investigation

6 HEBSUR & SATYANARAYANA 17 th WCSS, August 2002, Thailand References Brar, M.S., A. Subba Rao and G.S. Sekhon Journal of Potassium Research 2: Ghosh, S.K. and N.P. Datta Proceedings of the Indian National Science Academy. 40 B: 138. Jackson, M.L Soil Chemical Analysis. Prentice Hall of India, New Delhi. Patiram and R.N. Prasad Journal of the Indian Society of Soil Science 39: