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ThesisItem Open 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, MaramiAn 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.ThesisItem Open Access PEDOGENIC CHARACTERIZATION OF PADDY AND ASSOCIATED NON-PADDY SOILS OF ASSAM(AAU, Jorhat, 2018) Mohanty, Shraddha; Karmakar, Rajendra MohanAn 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.ThesisItem Open Access ALUMINIUM AND PHOSPHATE POTENTIAL IN ACID SOILS OF ASSAM(AAU, Jorhat, 2018) Borah, Supriya; Bhattacharyya, DevajitThe 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.ThesisItem Open Access FORMULATION OF LIQUID RHIZOBIAL BIOFERTILIZER AND ITS VALIDATION(AAU, Jorhat, 2018) Bharali, Happy; Baruah, RajenThe 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.ThesisItem Open Access DYNAMICS OF ZINC FRACTIONS AND AVAILABLE NUTRIENTS AS INFLUENCED BY ZINC FERTILIZATION ON RICE CULTIVARS(AAU, Jorhat, 2018-07) Baishya, Bhupen Kumar; Basumatary, A.A field experiment was carried out at the Instructional-cum-Research (ICR) farm, Assam Agricultural University, Jorhat during Kharif season, 2014 and 2015 to study the influence of zinc fertilization on the dynamics of zinc fractions, available nutrients status in the soil and crop yield and quality of rice grain of different cultivars. The treatments consisted of zinc applied through soil with or without foliar spray and five different rice cultivars. Total of twenty treatment combinations were laid out in factorial RBD with three replications. Distribution of different zinc fractions in soil were assessed during different stages of crop period of rice. Perusal of experimental findings showed that zinc fertilization exerted a significant positive effect on different zinc fractions in the soil during both the years of investigation. Among zinc treatments, concentration of all the zinc fractions were maximum with application of Zn @ 5 kg ha-1 + 0.5% foliar spray of Zn over other treatments. The study revealed that the concentration of the water soluble plus exchangeable Zn, complexed-Zn and crystalline sesquioxide bound-Zn fractions showed a decreasing trend from tillering stage to the harvest stage of the crop, while, availability of amorphous sesquioxide bound Zn, residual-Zn and total-Zn fractions followed an increasing trend with respect to concentration with the advancement of time. Among the zinc fractions, water soluble plus exchangeable form made the lowest contribution while residual fraction made the highest contribution to the total zinc pool than other fractions of Zn at all the growth stages of the crop. At harvest, zinc concentration in various fractions of Zn in soil varied in the following order: watersoluble plus exchangeable < complexed < crystalline sesquioxide bound < amorphous sesquioxide bound < residual fraction< total zinc. There was significant positive correlation among the Zn fraction in soil indicating existence of dynamic equilibrium of Zn in soil. The available fraction of all nutrients was initially higher and gradually decreased with advancement of crop growth. The maximum availability was obtained at tillering stage and thereafter as crop age advanced nutrient availability decreased. Analysis of pooled data revealed that application of Zn @ 5 kg ha-1 in soil + 0.5% foliar spray resulted in higher availability of nitrogen, potassium, sulphur and DTPAZn in soil at different stages of crop and recorded highly significant and positive correlation with different zinc fractions. Availability of phosphorus, DTPA-Fe, DTPAMn and DTPA-Cu were decreased with zinc application and the lowest content was found at treatment Zn @ 5 kg ha-1 in soil + 0.5% foliar spray and exhibited a significant but inverse correlation with different zinc fractions. Zinc fertilization influenced the crop yield and nutrient uptake. Highest grain yield was recorded in treatment receiving Zn @ 5 kg ha-1 + 0.5% foliar spray of Zn (53.40 q ha-1) and the lowest was in control (38.69 q ha-1). Among the cultivars, variety JKRH-401 recorded the highest grain yield (64.27 q ha-1) whereas variety Kolajoha recorded the lowest grain yield (30.50 q ha-1). Among different treatment combinations, application of Zn @ 5 kg ha-1 + 0.5% foliar spray of Zn in combination with cultivar JKRH-401 recorded the highest yield (71.82 q ha-1) . The highest straw yield was recorded in treatment receiving Zn @ 5 kg ha-1 + 0.5% foliar spray of Zn. Among the cultivars, the highest straw was recorded in JKRH-401(71.22q ha-1) while, the lowest was found in Aghunibora(49.27 q ha-1). Uptake of nitrogen, potassium, magnesium and sulphur by rice was significantly influenced by Zn-fertilization and the highest was found in treatment with treatment receiving Zn @ 5 kg ha-1 and 0.5% foliar sprays of Zn over other treatments. On the other hand, in respect of copper and manganese, application Zn @ 5 kg ha-1 and 0.5% foliar spray of Zn resulted the lowest uptake during all crop growth period. The cultivars, JKRH-401 recorded the highest uptake of all the nutrients at all stages of crop growth. In economic terms, combined application of Zn @ 5 kg per ha and 0.5% foliar spray of Zn in combination with cultivars, JKRH- 401 recorded the highest gross return, net return and B:C ratio (2.96 ). Zinc fertilization had significant impact on the nutrient content in both brown and polished rice grains. The treatment receiving Zn @ 5 kg ha-1 + 0.5% foliar spray of Zn recorded the highest concentration of nitrogen, potassium, sulphur and zinc for both brown and polished rice. Protein content was found to be the highest in treatment receiving Zn @ 5 kg ha-1 + 0.5% foliar spray of Zn and cultivar JKRH-401 exhibited the highest content of 10.71 % and 8.75 % in brown and polished rice, respectively. Highest amylase content (18.73 % and 20.42 %) was observed in same treatment and the cultivar Kolajoha recorded the highest amylase of 22.52 % and 24.16% in brown and polished rice, respectively.
