The effcts of different waterlogging periods on morphology and clay mineralogy of paddy soils

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1 Symposium no. 18 Paper no. 359 Presentation: poster The effcts of different waterlogging periods on morphology and clay mineralogy of paddy soils BAHMANIAR M.A. and MIRNIA S. KH. Dept. of Soil Science, Sari College of Agricultural Science, Mazandaran University, P. O. Box 578, India Abstract The effect of different rice plantation periods on the properties of selected soils in alluvial plain was studied. The soils have been under continuous rice cultivation for less than 10 years, years, years, and over thirty-years period. In each rice cultivated and non-rice cultivated fields a soil profile and two nearby auger holes were studied. Soil samples were taken from different horizons and layers of the soil profiles and auger holes. Morphological features of each soil profile were determined and soils were classified according to USDA, soil taxonomy. Soil samples were analyzed by conventional methods and clay minerals were identified by X-ray diffraction analysis. This study indicated that continuous rice cultivation changed soil moisture regime from xeric to aquic and soil color also became greyish, surface horizons changed from mollic to ochre epipedons. With increasing period of cultivation soil mottle increased and soil structure became massive. Therefore the soil classificationmodified from mollisols to inceptisols. No illuviation and eluviation of clay minerals occurred as a consequence periods of rice cultivation. X-ray diffraction analysis showed that clay minerals in nonrice cultivated field were illite, vermiculite, montmorillonite, kaolinite, chlorite and in rice field were illite, montmorillonite, kaolinite and chlorite respectively. But with increasing the period of cultivation, the amount of illite decreased and montmorillonite increased. Keywords: paddy soils, morphology, clay mineralogy, period, waterlogged Introduction Rice is one of the major food crops in Iran and had been dominantly grown in alluvial, flood and piedmont plains of the southern coast of the Caspian Sea in the provinces of Gilan, Mazandaran and Golestan. The area under rice cultivation in these three provinces is about 450,000 ha. Submergence, Puddling and continuous (without rotation) are common practices in rice cultivation. These practices have significant effects on the properties of paddy soils. In rice cultivation under flooded condition temporary` and permanent changes were distinguished. Temporary changes were limited to surface soils and are associated with puddling as practised in many paddy fields and also with alternating chemical oxidation and reduction. Although, these temporary surficial edaphic changes are important from the point of view of crop management and production do not change the taxonomic classification of soils by themselves. However, the cumulative effect of these recurrent temporary changes may lead to more permanent changes of the pedon, and possibly to a change in the taxonomic classification. Changes which may lead to the alteration of the taxonomic 359-1

2 classification of soils under flooding for rice cultivation may be grouped into three categories: i. Changes due to agricultural engineering; ii. Changes in the soil moisture regime; iii. Changes due to the alteration or neoformation of genetic horizons (Nelson, 1982). Changes in physical properties as a result of flooding and puddling, and the associated development of a plowpan, are beneficial for rice growth in that they improve nutrient availability and reduce percolation (Neue, 1988b). Texture, mineralogy and organic matter content determine soil structure and greatly influence nutrient kinetics (Neue, 1988c). The relationship between the mineral composition of a clay fraction in paddy soils, the type of parent materials and their geomorphology was examined by Xu-Yang and Jiang (Xu et al., 1981). They concluded that when the paddy soils are derived from the new alluvial deposits, hydrous micas and smectite predominat. Paddy soils showed greying and mottling in the plough layer and plough pan. There was no downwared movement of silt and clay due to physical weathering by alternate oxidation-reduction and freeze-thaw effects (Moormann, 1981). Cultivation to paddy fields increased the ph, organic matter content, potassium and phosphorus cocenterations of the soil (Jackson, 1975). Change in soil processes caused by rice cultivation were studied. The changes include clay removal from the arable horizon, as well as changes in mineralogical composition. Disintegration of smectite, and a relative accumulation of quartz were observed in these plastic aquazems, with individual smectite predominant in their fraction <1 m (77-96%) together with kaolinite-smectite (4-23%) (Shishov et al., 1996). Soil color became greyish, soil structure becam massive, the formation of soil mottles and concretions, a tendency to strongly reducing condition, unchanged soil texture (Nelson and Sommers, 1982). Materials and Methods The area studied was located in Mazandaran province. Average annual precipitation is 700mm and most of the rain falls during the autumn and winter periods. Average annual temperature is about 16. Based on soil survey reports, in the alluvial plain five fields (non-rice cultivated, cultivated less than 10 years, years, years and over thirty years period continuous rice cultivation) that were located within the similar mapping unit have been selected. A soil profile and two auger holes from rice cultivated and non-rice cultivated fields were chosen and soil samples were taken from different layers in October. Morphological characteristics of each soil profile were determined in the field, and soils were classified according to USDA, soil taxonomy (Neue, 1988c). Soil samples were air-dried, particle size analyses of the soil samples were determined by the hydrometer method (Jiang et al., 1993). Chemical analyses were performed on soil samples which had been ground by an electric mill and passed through a 10 mesh sieve. The ph value of the saturated paste was measured by a glass electrode (Munir, 1998). Carbonates were determined by the acid neutralization method (Gee and Baude, 1986). Organic carbon was measured by the Walkley and Black method (Chen Ming et al., 1994). Clay minerals were separated from soil samples after the removal of soluble salts, carbonates and organic matter as described by Jackson (Mclean, 1982). Clay samples were saturated with Ca and K using 1 N CaCl 2 and KCl, respectively. Ca-Saturated clays were also solvted by ethylene glycol and K-Saturated clays heated at 550 o C for five hours. The clay minerals were then identified by X-ray diffraction analysis (Jackson, 1975)

3 Results and Discussion The morphological characteristics of the soils studied are shown in Table 1. The soils were derived from alluvial materials and did not show any significant development. Since illuvial and eluvial processes were not so influential, no translocation of clays and other materials occurred in the soil profiles (Moormann, 1981). Mollic and ochric epipedons were also the main surface horizons and a cambic horizon was the only subsurface diagnostic horizon identified (Nelson, 1982). The soils were generally medium to fine textured and unchanged. Morphological changes of soil affected paddy soil classification, because the soi classification systems consider soil morphogenetic qualities (Nelson and Sommers, 1982). The physico-chemical characteristics of the soils studied are shown in Table 2. The amount of clay in the surface horizons varied from 35 to 44%. Translocation of clay was not observed in any of the soils studied. The soils and their parent materials were generally alkaline and ph values were mostly above 7.0 in both rice and non-rice cultivated soils. The amounts of CaCO 3 in the soil profiles varied from 17.5 to 25% and there were no significant differences between paddy and other soils. Organic matter content of the soil profiles ranged from 1.23 to 2.5% but increased in paddy soils (Jackson, 1975). X-ray diffraction analysis of different soil horizons indicated that illite was one of the major clay minerals in both paddy and non-paddy soils. Diffuse and very low intensity peaks at 10 A, which has been under long and continuous rice cultivation, indicated the transformation of degraded illite into other 2:1 expansible clay minerals. This has been confirmed by the occurrence of strong, sharp peaks at about 19A in the ethylene glycol solvated specimen (Figures 1, 2). Intensities of 10A peaks increased by increasing soil depth. Vermiculite clay mineral was identified in non-paddy soils by peaks at about 15A in the ethylene glycol solvated clays, which collapsed to 10 A after potassium saturation (Figure 1). However, the transformation of vermiculite into montmorillonite in the surface and subsurface horizons of paddy soils was indicated by the disappearance or weakening of the 14 and 15 A peaks in the ethylene glycol solvated specimen (Cheng et al., 1994; shishov et al., 1996) (Figures 1, 2). Montmorillonite was one of the major clay minerals in most of the soils studied. This has been indicated by relatively strong peaks at 18 to 19 A in the ethylene glycol solvated clays and A in the K-saturated clay samples. Peaks at 7.2 and 3.6A, which collapsed due to potassium saturation and heating at 550 o C, indicated the small amount of kaolinite in most of the soils. However, small amounts of chlorite or hydroxy-interlayered clay minerals were also identified in some soils by the presence of stable 13 to 14 A peaks in the K-saturated and the 550 o Cheated samples (Figure 2)

4 Table 1 Morphological Characteristics of the soil profiles in different waterlogging period. Horizon Depth (cm) Color (Moist) Texture Structure Consistenec (Moist/wet) Boundary Other soil Characteristics Pedon No. 1 clayey, mixed, thermic, typic haploxerolls (non - paddy soils) Ap YR3/2 sicl gr fi CS Bw YR3/2 sicl 1mabk,2 fi CS mabk Bw YR 3/2 sicl 1mabk, fi CS 2mabk C YR 4/4 sicl 1msbk fi CS C YR 4/4 sicl gr fi Pedon No. 2 Fine, mixed, thermic, mollic epiaquepts (<10 years waterlogged) Apg YR 3/3 sic m fi CS mottling present in Bwg YR 4/3 sic m fi CS all horizons 7.5 YR3/4 C1g YR 4/4 sic m fi CS gleyzation begins in C2g YR 5/4 sic m fi CS Apg horizon 5Y 5/1.5 C3g YR 4/4 sic m fi in 20% matrix Pedon No. 3 Fine, clayey, thermic, mollic epiaquepts (10-20 years waterlogged) Apg YR 5/2 sil m fi CS mottling present in Bwg YR 4/1 cl m fi CS all horizons7.5yr3/4 C1g YR 5/2 cl m fi CS gleyzation begins in C2g YR 4/2 cl m fi Apg horizon in 20% to 50% matrix Pedon No. 4 clayey, mixed, thermic, mollic epiaquepts (20-30 years waterlogged) Apg YR 4/1 sicl m fi CS mottling present in all C1g YR 5/1 sicl m fi CS horizon gleyzation C2g YR 5/2 sicl m fi CS begins in Apg C3g YR 5/1 sicl m fi CS horizon and persists C4g YR 5/2 sicl m fi through the solum 5Y5/1.5 Pedon No. 5 Fine, mixed, thermic, mollic epiaquepts (> 30)ears waterlogged ) Apg YR 4/2 sicl m st.p CS motting present in C1g YR 4/1 sicl m st.pl CS all horizons, gleyzation C2g YR 4/1 sicl m st.pl CS begins in Apg horizon C3g YR 4/2 sic m vst.pl CS and persists through C4g YR 3/1.5 sic m vst.pl the solum 5Y5/

5 Table 2 Some physico-chemical characteristics of the soils studied. Depth (cm) sand silt clay ph CaCo 3 eq OM Pedon no Pedon no Pedon no Pedon no Pedon no

6 Figure 1 X-ray diffraction patterns of clay minerals of peadons No.1, 3: A) Casaturation, B) Ethylene glycol solvated, C) K- saturation, D) K- saturation o C heated

7 Figure 2 X-ray diffraction patterns of clay minerals of peadons No.4: A) Casaturation, B) Ethylene glycol solvated, C) K- saturation, D) K- saturation o C heated. Conclusions Due to cotinuous rice cultivation and yearly paddling, soil color underwent a change and became grayish (Nelson and Sommers, 1982). By increasing the period of cultivation the soil moisture regime changed from xeric to aquic, surface horizons changed from mollic to ochric epipedon, soil structure became massive with poor drainage conditions, and soil mottles increased (Nelson and Sommers, 1982). X-ray diffraction analysis showed that there was a gradual disintegration of illite mineral and the rate of changes in the over thirty year continuous cultivation was higher than other paddy soils. Vermiculite clay mineral was identified in non-paddy soils but in paddy soils the disintegration or transformation of clay mineral occurred mainly in soils where in continuous rice cultivation (Jackson, 1975). The amount of montmorillonite in surface and subsurface horizons of paddy soils was higher than non-paddy soils which had the continuous rice cultivation. It is worth nothing that the disintegration or transformation of clay minerals occurred mainly in soils where the required conditions for this phenomenon, such as longer period of rice cultivation and relating good drainage, were available. The presence of chlorite in some horizons of paddy soils is probably attributed to free iron oxides interlayered in montmorillonite. References Chen Ming, L., C.M. Gengling and G.L. Liu Clay mineral composition, soil fertility and surface chemistry characteristics of quaternary red soils in Southern Hunan province. Scientia Agricultural Sinica 27(2): Gee, G.W. and J.W. Baude Particle-size analysis, pp In A. Klute (ed.). Methods of Soil Analysis, Part 1. 2 nd. ASA and SSSA, Madison, WI

8 Jackson, M.L Soil Chemical Analysis. Advanced course. Published by the author, Madison, WI. Jiang, Yz, Li Qm and S. Matsumoto Physicochemical properties and morphological characteristics of various paddy soils in northeast China. Japanese J. of Soil Sci. and Plant Nutr. 64(4): Mclean, E.O Soil ph and lime requirement, pp In A.L. Page (ed.). Methods of Soil Analysis, Part 2. 2 nd. ASA and SSSA, Madison, WI. Moormann, F.R The classification of paddy soils as related to soil taxonomy. Ibid. pp Munir, M Effects of paddy soil cultivation on changes in the soil morphology. Agrivita 18(1):1-6. Nelson, R.E Carbonate and gypsum, pp In A.L. Page (ed.). Methods of Soil Analysis, Part 2. 2 nd. ASA and SSSA, Madison, WI. Nelson, D.W. and L.E. Sommers Total carbon, organic carbon, and organic matter, pp In A.L. Page (ed.). Methods of Soil Analysis, Part 2. 2 nd. ASA and SSSA, Madison, WI. Neue, H.U. 1988b. Management of physical properties of soils. Paper Presented at the Fifth International Soil Management Workshop on Classification and management of Rice-Growing Soils. Taiwan, Roz. December Neue, H.U. 1988c. Holistic view of chemistry of paddy soils. A paper prepared for presentation at the First International Symposium on Soil Fertility. Chiang-Mai, Thailand December, Shishov, L., N. Chizhikova and O.S. Bagdasaryan Mineralogical composition of paddy soils of Mckong Valley. Eurasian Soil Sci. 28(10): Soil Survey Staff Key to Soil Taxonomy. SMSS. Xu, Ji-Guan, Yang De-Young and Jiang Mei-Yin Clay minerals of paddy soils in Taihu Lake region, pp In Institute of Soil Science (ed.). Proceedings of Symposium on Paddy Soils. Academia Sinica Science Prees, Beijing

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

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