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Subject: Soil Sciences × End date: 2018 × Start date: 2018 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    DISTRIBUTION OF PEDOGENIC IRON AND ALUMINIUM IN RELATION TO SOIL ACIDITY COMPONENTS UNDER DIFFERENT LAND USES IN GOLAGHAT DISTRICT OF ASSAM
    (AAU, Jorhat, 2018) Kalita, Pallabi; Dutta, Marami
    An investigation was carried out to study the pedogenic distribution of Fe and Al, the soil acidity components and to assess the relationship of pedogenic Fe and Al with soil acidity components under different land uses in Golaghat district of Assam. Five pedons were selected representing five land uses viz., Forest cover (P1), Paddy cultivation (P2), Tea plantation (P3), Bamboo plantation (P4) and Vegetable cultivation (P5) from Nambor Doigrung Reserve Forest, Borjan, Doria, Dergaon and Danichapori respectively. The dominant hue of soil colour was 10YR. Value ranged from 4 to 7 and chroma ranged from 1 to 6. Texture varied from sandy loam to clay loam in the surface and loam to clay in the sub-surface horizons. The structure of the soils varied from massive in the surface to sub-angular blocky to angular blocky in the subsurface. The clay content and bulk density increased with soil depth. The highest amount of organic carbon was recorded in A horizon of forest soil (P1) with 2.2 per cent. The pH were in acidic range in all the pedons and in all the cases ΔpH (pHKCl – pHH20) was negative. Among the exchangeable cations Ca2+ was the dominant followed by Mg²⁺, Na⁺ and K⁺. CEC ranged from 7.5 to 10.8 in the surface and 5.8 to 15.9 cmol (p⁺) kg⁻¹ in the sub-surface horizons. The percent base saturation generally tended to increase with depth with some exceptions in P1. Soils were classified as Typic Dystrudepts (P1, P3 and P4), Oxyaquic Hapludalfs (P2) and Aquic Udifluvents (P5). Dithionite extractable Fe (Fed) and Al (Ald) constituted the highest amount among the pedogenic iron and aluminium. Fed tended to increase with soil depth with few exceptions. On the weighted average, paddy soil (P1) recorded the highest Fed. Oxalate extractable iron (Feo), amorphous inorganic iron (Feo – Fep) was irregularly distributed in all the pedons. On the weighted average vegetable soil (P5) and paddy soil (P2) recorded highest (Feo) and (Feo – Fep) respectively. The distribution of (Fed – Feo) was irregular in all the pedons except P1. On the weighted average forest soil (P1) recorded the highest (Fed – Feo). The surface horizons recorded comparatively higher amount of pyrophosphate extractable iron (Fep) than the subsurface horizons in all the pedons. The amount of KCl extractable iron (FeKCl) was low which ranged from 0.001 to 0.002 per cent in all the pedons. The ammonium acetate extractable iron (FeNH4OAc) was below detectable limits in all the pedons. On the weighted average, Paddy soil (P2) recorded the highest dithionite extractable aluminium (Ald). Oxalate extractable aluminium (Alo), crystalline form of aluminium (Ald – Alo) and amorphous inorganic aluminium (Alo – Alp) followed inconsistent trend with soil depth whereas pyrophosphate extractable aluminium (Alp) decreased with soil depth. Bamboo soil (P4) recorded the highest Alo, bamboo soil (P4) and vegetable soil (P5) recorded highest Alp. Bamboo soil (P4) recorded highest (Alo – Alp) and forest soil (P1) recorded highest (Ald – Alo). The amount of ammonium acetate extractable aluminium (AlNH40AC) at pH 4.8 was low but was higher than that extracted by KCl solution. Profile weighted mean of forms of acidity under various land uses depicted that the paddy soil (P2) exhibited maximum extractable, non-exchangeable and hydrolytic acidity, tea soil (P3) exhibited maximum total acidity, exch. H+, exch. Al3+ and exchange acidity and bamboo soil (P4) exhibited maximum pH dependent and total potential acidity. It was observed that the soils under forest cover (P1) and vegetable cultivation (P5) exhibited lower acidity compared to other land uses in the present study. Principal component analysis of the 27 soil characters revealed that different forms of Fe and Al contributed towards development of soil acidity irrespective of land use. Among the physico-chemical parameters clay contributed positively and significantly and pH (pHH2O and pHKCl) contributed negatively and significantly towards soil acidity.
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    ThesisItemOpen Access
    PEDOGENIC CHARACTERIZATION OF PADDY AND ASSOCIATED NON-PADDY SOILS OF ASSAM
    (AAU, Jorhat, 2018) Mohanty, Shraddha; Karmakar, Rajendra Mohan
    An investigation was carried out to study the morphological, physical and chemical characteristics, clay-organic carbon complexes and pedogenic distribution of iron, manganese and aluminium in clay fraction of paddy and associated non-paddy soils of Assam. Four districts viz., Golaghat, Jorhat, Sivasagar and Dibrugarh in the Upper Brahmaputra valley of Assam were selected for the present study. Eight soil profiles four each from mono-cropped paddy and associated non-paddy areas were collected. Horizon-wise soil samples were analyzed for important soil properties and clay-organic carbon complexes and different forms of Fe, Al, Mn in clay fraction using standard procedures. Soil colour varied from dark gray to brownish yellow. Yellow (10YR 6/8) to light red (2.5YR 6/8) mottles were observed in the subsurface horizons of the soils. Texture of the soils ranged from loamy sand to clay and structure varied from massive to subangular blocky. Sand, silt and clay contents varied from 11.3-49.0, 21.5-50.8 and 26.2-56.9 per cent in paddy and 23.3-65.4, 11.4-42.9 and 14.4-44.4 per cent in non-paddy soils respectively. Organic carbon content in soil varied from 2.0-12.0 and 0.5-10.0 g kg-1 in paddy and non-paddy soils respectively. Bulk density of soils increased with soil depth, pH of the soils varied from 4.4-6.0 and EC was found to be low (0.11-0.20 dSm-1). CEC of soil varied from 7.5-14.1 cmol (p+) kg-1 in paddy and 5.1-12.7 cmol (p+) kg-1 in non-paddy soils having dominance of exch. Ca++ followed by Mg++, Na+ and K+. Base saturation of the soil was low (32.3 to 57.5%). Soils were classified as: Typic Epiaqualfs (P1), Aeric Epiaqualfs (NP1, P2, P3, NP3, P4), Ultic Hapludalfs (NP2) and Typic Dystrudepts (NP4). Clay-organic carbon complex (OCclay) varied from 2.41-15.5 g kg-1 in paddy soils and 0.71-13.80 g kg-1 in non-paddy soils. Results showed that OCclay constituted 37.18-65.60% of SOC in paddy soils and 31.60-54.62% of SOC in non-paddy soils. Humus C (CH-clay), humin C (CHN-clay) in the clay fraction was found to be higher in non-paddy soils, whereas humic acid C (CHA-clay) and fulvic acid C (CFA-clay) in clay fraction was higher in paddy soils than their counter parts. CHA-clay/CFA-clay ratio was observed to be less than 1 indicating dominance of fulvic acid in the clay-organic carbon complexes. 25 Total (Fet), dithionite extractable (Fed), pyrophosphate extractable iron (Fep) and manganese in clay fraction were slightly higher in non-paddy soils as compared to paddy soils whereas oxalate extractable iron and manganese showed a reverse trend. Fed formed major portion of total iron content in clay fraction (Fet) followed by Feo and Fep in both paddy and non-paddy soils. Crystalline iron oxide (Fed-Feo) and silicate iron (Fet-Fed) in clay fraction was found to be higher in non-paddy soils while amorphous inorganic form of iron (Feo-Fep) showed the reverse trend. Different forms of Mn showed similar trend as that of different forms of iron in clay fraction of both paddy and associated non-paddy soils. Total Al (Alt), dithionite extractable Al (Ald) and oxalate extractable Al (Alo) in clay fraction were slightly higher in paddy soils as compared to non-paddy soils whereas pyrophosphate extractable Al (Alp) showed a reverse trend. Ald formed major portion of total Al content in clay fraction (Alt) followed by Alp and Alo in both paddy and non-paddy soils. Crystalline Al oxide (Ald-Alo), amorphous inorganic Al (Alo-Alp) and silicate Al (Alt-Ald) in clay fraction was found to be higher in paddy soils than non-paddy soils. In the present investigation, variation in morphological, physical and chemical characteristics of soils, clay organic carbon fractions, distribution of various forms of Fe, Mn and Al in clay fraction were observed in the paddy and associated non-paddy soils of Assam. Low amount of sand and high amount of clay in paddy soils as compared to non-paddy soils indicate more intense weathering in paddy soils due to anthropogenic factors and agro-hydrological regimes. Most of the paddy soils exhibited aquic characteristics leading to process of gleization. Formation of more amounts of clay-organic complexes was also observed in the paddy soils. Further studies are needed using modern tools (SEM, IR, X-ray etc.) for detailed pedogenesis and mechanisms in clay-organic complex formation in paddy and associated non-paddy soils of Assam.
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    ThesisItemOpen Access
    ALUMINIUM AND PHOSPHATE POTENTIAL IN ACID SOILS OF ASSAM
    (AAU, Jorhat, 2018) Borah, Supriya; Bhattacharyya, Devajit
    The study was carried out to investigate the “Aluminium and Phosphate Potential in Acid soils of Assam”, with the objectives 1) Determine different form of aluminium and phosphorus in Upper Brahmaputra Valley Zone (UBVZ) of Assam and 2) Determine aluminium and phosphate potential in soils of UBVZ of Assam. For this study twenty (20) surface (0-15 cm) soil samples were collected from Sivasagar, Golaghat and Majuli district of Assam. The soils were analyzed for different parameters pertaining to this investigation following standard procedures and laboratory protocols. The soils were varied widely in texture (sandy clay loam to clay), clay content (13 - 40%), pH (H2O) (4.02-7.49), pH (KCl) (3.10 to 6.89), OC (0.59-2.85%), CEC (6.75 to 12 cmol (p+) kg-1), free oxides of iron (3.78 to 1.09%) and aluminium (1.17 to 0.32%), lime potential (3.04 -5.85). The results on forms of acidity revealed that TPA (7.05 cmol (p+) kg-1) was the most dominant form of acidity in soils UBVZ of Assam followed by PDA (5.13 cmol (p+) kg-1), Ext.A (3.16 cmol (p+) kg-1), TA (1.92 cmol (p+) kg-1) = Ex.A (1.92 cmol (p+) kg-1) and Non Ex.A (1.22 cmol (p+) kg-1). Among the forms of Al, the CBD extractable aluminium (Ald) was found to be the most dominant followed by oxalate extractable Al (Alo), weakly organically bound Al (Alw), totally organically bound Al (Alp) and exchangeable Al (AlKCl), with mean values 0.38,0.22, 0.09, 0.02 and 0.01per cent, respectively. The amorphous form of aluminium showed dominance over the crystalline form of aluminium. The Organic phosphorus of the soils ranged from 164.68 to 345.62 mg kg-1. Different inorganic P fractions of the soils were found in the order: Fe-P (68.2-20.4 mg kg-1) > Al-P (42.9-19.7 mg kg-1) > Occl-P (20-11 mg kg-1)>Ca-P (10.2-17.6 mg kg-1) > Re-P (15.6-9.2 mg kg-1)> Sal-P (2.3-10.2 mg kg-1). The percent release Al (%RelAl) decrease with increase in added Al irrespective of the soil studied. The highest and lowest %RelAl was observed in soil S4 of Sivasagar district and soil M3 of Majuli district, respectively. The decrease in %AdsP was ranged from 97.6 to 7.00 per cent in soils of UBVZ of Assam when addition of P was ranged from 1 to 5 mg l-1. The highest % AdsP was found in soil S1 of Sibsagar district, with a mean value of 97.11 per cent. The lowest mean % AdsP (15.98 %) was found in soil UM6 of Majuli. P released was observed at equilibrium solution of soil S8 of Sivsagar district and soil M3 of Majuli district at the lowest concentration of add P i.e. 1 mg l-1. In soil UM5 and UM6 of Majuli district % RelP was observed from 1 to 3 mg l-1 of add P. In all these soils % RelP was decreased with increased in addition of P. The mean value of % RelP in soils of UBVZ ranged from 20.64 to 30.89 per cent. The soil UM5 (24.32) of Majuli district had the highest aluminium potential and the same was the lowest in soil S4 (16.08) of Sivsagar district. Equilibrium aluminium potential (EAP) of the soils showed very high significant positive correlation with pH (H2O) and pH (KCl) (r=0.865** and r=0.735**) and very significant negative correlation with oxides of iron and aluminium (r=-0.819** and r=-0.850**). EAP of the soils also had negative correlation with all forms of acidity and exchangeable aluminium. The highest phosphate potential was observed in soil S1 (5.30) of Sivsagar district while lowest was observed in soil UM5 (0.70) of Majuli district. In these soils equilibrium phosphate potential (EPP) had a significant negative correlation with soil pH (H2O) (r=-0.956**) and pH (KCl) (r=-0.858**), and significant positive correlation with oxides of iron (r=0.938**) and oxides of aluminium (r=0.963**). Significant positive relationship of EPP was also observed with all forms of acidity except non exchangeable acidity. While a significant positive correlation was observed with Fe-P (r=0.791**), Al-P (r=0.733**), Occl-P (r=0.930**) and RS-P (r=0.500*). However, EPP of the soils had significant negative relationship with Org-P (r=-0.560**), Ca-P (r=-0.849**) and Sal-P (r=0.857**). The correlation of EPP with EAP and lime potential (LP) of the soils was significant and negative (r=-0.969** and r=-0.872**), respectively. In soils of UBVZ of Assam if EAP and LP were high the equilibrium phosphate potential will be low indicating higher availability of phosphorus, as increase of LP and EAP also increase the pH of the soils. Therefore, liming and addition of organic matter might be considered good management practices for these acid soils to increase the pH as well as to increase the Phosphorus availability.
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    ThesisItemOpen Access
    FORMULATION OF LIQUID RHIZOBIAL BIOFERTILIZER AND ITS VALIDATION
    (AAU, Jorhat, 2018) Bharali, Happy; Baruah, Rajen
    The present study on “Formulation of liquid rhizobial biofertilizer and its validation” was carried out in the laboratory of the Biofertilizer Production Unit, Department of Soil Science, Assam Agricultural University, Jorhat during 2017-18. The objective of this investigation was to determine the shelf-life of the liquid formulation, to study the nodulation pattern and establishment of added rhizobia in specific host legumes and to ascertain the validation of the effective liquid formulation on pea, green gram and black gram. The experiment was laid in a Completely Randomised Block Design. The individual strains of greengram(Rhiz-10) and blackgram(Rhiz-13) was diluted to different formulations of 25, 50, 75 and 100 per cent and shelf-life was examined in comparision with a solid substrate at 0, 30, 60, 90 and 120 days of incubation. Results showed that viable population of rhizobia could be maintained with different formulations even upto 120 days. Whereas, in solid substrate the viable population started decreasing more, as days of incubation increased irrespective of pulse crops . The colony forming unit in 100 per cent liquid formulation ranged from 1.2 to 3.2x108 cfu/ml in greengram and 1.7 to 2.4x108 cfu/ml in blackgram from 0 to 60 days of incubation. Nodulation pattern was studied in terms of infectivity test for three crops viz. pea, greengram and blackgram under sterile condition using Gibson tube method. The three rhizobial strains (Rhiz-25, Rhiz-10 and Rhiz-13) of different concentrations of 25, 50, 75 and 100 per cent was prepared and inoculated in tubes and some tubes were kept as control. At 20th day of inoculation, nodule number, nodule dry weight and establishment (cfu/nodule) was found to be highest for all the three crops on application of 100 per cent liquid formulation. The establishment of rhizobia per nodule at 100 per cent liquid formulation for pea, green gram and blackgram was recorded to be 5.6, 7.3 and 5.0x103 cfu/nodule respectively. For validation, a pot culture study was conducted using pulses like pea, greengram and blackgram under unsterile condition with respective rhizobial formulation of 50 and 100 per cent concentration. The replicated plants were grown for 60 days and thereafter harvested. The results showed that nodulation pattern (nodule number and dry weight), and yield parameters increased significantly over uninoculated control at 50 and 100 per cent formulation. Rhizobia got well established in treated pots. Further, enzyme activities of the soil with respect to inoculated crops also increased indicating enhanced rhizobial activity. The numerical data on yield recorded for pea, greeengram and blackgram were 25, 18 and 12 pods per plant at 100 per cent rhizobial formulation. Similarly, enzyme activities also increased from 26.66 to 35.52 μg TPF g-1 24 h-1 DHA, 1.63 to 2.57 μg fluorescein g-1 30 mins-1 FDA and 12.12 to 16.58 μg p-nitrophenol/gm/hr PMEase for soil grown with pea at 100 per cent rhizobial formulation and similar trend of result also showed in soil planted with greengram and blackgram.