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Assam Agricultural University, Jorhat

Assam Agricultural University is the first institution of its kind in the whole of North-Eastern Region of India. The main goal of this institution is to produce globally competitive human resources in farm sectorand to carry out research in both conventional and frontier areas for production optimization as well as to disseminate the generated technologies as public good for benefitting the food growers/produces and traders involved in the sector while emphasizing on sustainability, equity and overall food security at household level. Genesis of AAU - The embryo of the agricultural research in the state of Assam was formed as early as 1897 with the establishment of the Upper Shillong Experimental Farm (now in Meghalaya) just after about a decade of creation of the agricultural department in 1882. However, the seeds of agricultural research in today’s Assam were sown in the dawn of the twentieth century with the establishment of two Rice Experimental Stations, one at Karimganj in Barak valley in 1913 and the other at Titabor in Brahmaputra valley in 1923. Subsequent to these research stations, a number of research stations were established to conduct research on important crops, more specifically, jute, pulses, oilseeds etc. The Assam Agricultural University was established on April 1, 1969 under The Assam Agricultural University Act, 1968’ with the mandate of imparting farm education, conduct research in agriculture and allied sciences and to effectively disseminate technologies so generated. Before establishment of the University, there were altogether 17 research schemes/projects in the state under the Department of Agriculture. By July 1973, all the research projects and 10 experimental farms were transferred by the Government of Assam to the AAU which already inherited the College of Agriculture and its farm at Barbheta, Jorhat and College of Veterinary Sciences at Khanapara, Guwahati. Subsequently, College of Community Science at Jorhat (1969), College of Fisheries at Raha (1988), Biswanath College of Agriculture at Biswanath Chariali (1988) and Lakhimpur College of Veterinary Science at Joyhing, North Lakhimpur (1988) were established. Presently, the University has three more colleges under its jurisdiction, viz., Sarat Chandra Singha College of Agriculture, Chapar, College of Horticulture, Nalbari & College of Sericulture, Titabar. Similarly, few more regional research stations at Shillongani, Diphu, Gossaigaon, Lakhimpur; and commodity research stations at Kahikuchi, Buralikson, Tinsukia, Kharua, Burnihat and Mandira were added to generate location and crop specific agricultural production packages.

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  • ThesisItemOpen Access
    SYNTHESIS, CHARACTERIZATION AND RELEASE OF NANO-ENABLED PHOSPHORUS FERTILIZER IN ACID SOILS OF ASSAM
    (2021) Pachani, Sukanya; Kandali, Gayatri Goswami
    The study on “Synthesis, characterization and release of nano-enabled phosphorus fertilizer in acid soils of Assam” was undertaken during 2019-21with the aim to synthesize and characterize zeolite based nano P fertilizer and to study its release pattern over 90 days of incubation in three different types of soil representing major soil orders of Assam, taking recommended fertilizer dose applicable for maize. Surfactant modification of the zeolite (SMZ) was done by using hexadecyltrimethylammonium bromide (HDTMABr) as surfactant and subsequently, the slow-release fertilizer (SRF) for phosphorus was synthesized by treating the SMZ with potassium dihydrogen orthophosphate to prepare the P-loaded SRF. It was observed from the XRD pattern that the zeolite framework had not undergone major structural change by the addition of HDTMABr and the crystallinity of zeolite remained the same. The surface morphology characterized by SEM, showed that the zeolite was of cubical geometry. The developed zeolite based nano P fertilizer recorded an average particle size of < 100 nm. The specific surface area of nano zeolite fertilizer (modified) was found to be less (90.07 m2/g) as compared to unmodified zeolite (262.72 m2/g). The pore diameter was found to be in the microporous (< 20 nm) range. Maximum adsorption of 7.4% added P was found in nanofertilizer which was 60% higher as compared to unmodified zeolite. The incubation study of P release in different treatments over the different types of soil witnessed marked variations during the entire days of incubation. Although no definite trend was observed in absolute control all throughout the incubation period, the lowest concentration of P was found in 7 days of incubation in all the treatments. In treatment receiving recommended dose of P through SSP, there was a gradual rise in available P concentration, reaching the maximum peak at 32 days of incubation beyond which no further increasing trend was observed. Relatively, the treatment receiving recommended dose of P through nano-fertilizer had a gradual increase of P from 7 days upto 90 days of incubation. A similar trend was also observed in nano treated P fertilizer receiving 2.5 times reduction, 5 times reduction, and 10 times reduction from the recommended dose. However, the concentration of release was lower and found to be in decreasing order as compared to recommended P level applied through nano P. Highest concentration of P at 90 days of incubation was found in recommended P applied through nano-fertilizer in the silty clay loam soil (8.82 mg/kg), which was significantly higher than recommended P applied through SSP (7.54 mg/kg). A significant difference was also noticed between recommended dose of phosphorus applied through nano P (8.82 mg/kg) and treatment receiving 2.5 times reduction of recommended P from nano P (6.38 mg/kg). The same trend of P release was observed in the soil with clay loam and sandy clay loam texture. The differences in clay content between the soils affected the P release pattern which followed the order - Majuli (sandy clay loam) > Jorhat (silty clay loam) > Titabar (clay loam).The first-order kinetic constant was found to increase from 0.096 μg/g/day in recommended dose of P applied through SSP to 0.100 μg/g/day in treatment having a 10 times reduction of recommended P given through nano P in the silty clay loam soil. In the case of second-order kinetics, there was a decrease in rate constant value (-0.015 to - 0.014 g/μg/day) which means an increase in the release of P. The rate constant of parabolic diffusion equation was the highest in treatment receiving recommended dose of P through nano-fertilizer (3.012 μg/g/day) in the silty clay loam soil. This increase in rate constant was found in the clay loam and sandy clay loam soil also which indicated high reactivity of the fertilizer. As observed from the R2 value, the parabolic diffusion equation was found to be the best fit for describing the P release as compared to the other two kinetic models.
  • ThesisItemOpen Access
    SOIL FERTILITY STATUS IN RELATION TO FALLOW CYCLE IN SHIFTING CULTIVATED AREAS OF DIMA HASAO
    (2021) NUNISA, BAOSRING; Borkakati, Kabindra
    The present investigation was carried (2019-20) to study the effect of jhum fallow cycle on soil properties in the DIMA HASAO district of Assam. Total of 120 geo-referenced soil samples were collected from short jhum (1-3 yrs.) fallow cycle, medium jhum (4-6 yrs.) fallow cycle, long jhum (7-9 yrs.) fallow cycle and undisturbed soil. The collected soil samples were analyzed for parameters like pH, OC, N, P, K, S, Ca, Mg, CEC, HWS-B, and soil texture. The studied soil samples showed wide variations in texture varying from sandy loam to clay loam. Coarse texture sand was found to be dominant in short jhum and medium jhum while finer particles (silt and clay) were dominant in the long jhum and the undisturbed soil. The Soil pH was found lowest (mean value 4.55) in short jhum and highest (mean value 5.00) in the undisturbed soil. The OC content was minimum at initial short jhum fallow cycle (mean value 0.98%) and maximum was observed in the Undisturbed soil (mean value 1.55%). The CEC of the study area was found highest in undisturbed soil [mean value 8.64 cmol (p+) kg-1] followed by long jhum [mean value 7.98 cmol (p+) kg-1] medium jhum [6.83 cmol (p+) kg-1] and finally by short jhum [mean value 6.53 cmol (p+) kg-1]. The Avl. N content of the study area was found low to medium. Among the jhum fallow cycle Avl. N of short jhum was lowest (mean value 269.30 kg ha-1) followed by medium jhum (mean value285.64 kg ha-1), long jhum (mean value 335.84 kg ha-1) and highest in undisturbed soil (mean value 350.11 kg ha-1). The Avl. P content of the study area was found low to medium. Among the jhum fallow cycle, highest (mean value 12.61 kg ha-1) was observed in long jhum fallow cycle followed by Undisturbed soil (mean value12.03 kg ha-1), medium jhum (mean value 9.55 kg ha-1) and lowest in short jhum (mean value 9.33 kg ha-1). The available K content was found medium to high. Among the jhum soil the lowest mean value was observed in short jhum (169.46 kg ha-1) followed by medium jhum (217.89 kg ha-1), long jhum (244.02 kg ha-1) and the highest in the undisturbed soil (264.40 kg ha-1). The highest content of Avl. S was observed in long jhum fallow cycle (mean value 17.48 kg ha-1) followed by undisturbed soil (mean value 17.32 kg ha-1), medium jhum (mean value 16.09 kg ha-1) and lowest in the short jhum (mean value 13.43 kg ha-1). The highest of Ex. Ca was found in the undisturbed soil [mean value 1.78 cmol (p+) kg-1] followed by long jhum [mean value 1.46 cmol (p+) kg-1], short jhum [mean value 1.40 cmol (p+) kg-1] and lowest in the medium jhum [mean value 1.37 cmol (p+) kg-1]. The highest value of Ex. Mg was found in the undisturbed soil [mean value 1.19 cmol (p+) kg-1] followed by long jhum [mean value 1.09 cmol (p+) kg-1], short jhum [mean value 0.60 cmol (p+) kg-1] and the medium jhum [mean value 0.59 cmol (p+) kg-1]. HWS-B was found highest in undisturbed soil (mean value 0.94mg ha-1) followed by long jhum (mean value 0.81 mg ha-1), medium jhum (mean value 0.70 mg ha-1) and lowest in the short jhum fallow cycle (mean value 0.53 mgha-1). All the soil fertility parameters i.e., N, P, K, S, Ca, Mg, and B exhibited significant positive correlation with pH, OC, CEC, and percent Clay. The highest SQI was observed in the undisturbed soil 24.12 followed by long jhum 23.97, medium jhum 22.03 and lowest in the short jhum 21.46 fallow cycle. Thus, it could be concluded that the minimum jhum fallow cycle should be at least 7 to 9 years.
  • ThesisItemOpen Access
    SOIL BORON FRACTIONS AS INFLUENCED BY SELECTED SOIL PROPERTIES AND CROPPING SYSTEM IN BOKO BLOCK OF KAMRUP (RURAL) DISTRICT OF ASSAM
    (2021) Baruah, Neelom; Tamuly, Danish
    The present study was conducted with the twin objective to assess the influence of basic soil physico-chemical properties and cropping system (CS) on soil boron fractions in Boko Block of Kamrup (Rural) District of Assam. A total of twenty- four (24) geo-referenced surface soil samples (0-15 cm) were collected from across the blocks under each cropping system viz., Rice-Rice, Rice- Fallow, Vegetable-Vegetable and Plantation crops. The soil groups were found to vary in their physico-chemical properties irrespective of cropping system practised. The studied soil samples showed wide variations in texture varying from sandy clay loam (SCl) to clay loam (Cl). The ranges for pH, SOC (%), Av. Nitrogen (kg ha-1), Available P2O5 (Kg ha-1), Available K2O (Kg ha-1), CEC [Cmol (p+) kg-1], EC (dSm-1) ranged between very strongly acidic to strongly acidic (4.7-5.6), medium to high (0.6-1.6 %), Low to Medium (175.6-326.4 kg ha -1), Low to High (5.93- 57.68 kg ha -1), Medium (130.8-276.2 kg ha -1), Low (2.8-9.6 Cmol (p+) kg-1), Normal range (0.01- 0.03 ds m-1) respectively. The selected properties viz., CEC, pH and SOC were chosen based on past research findings to analyze its effect on soil boron fractions. Each of the three parameters were split in two groups: CEC (two groups-2.8-5.8 and 5.9-9.6 C mol(p+) kg-1), pH (two groups- 4.7-5.0 and 5.1-5.6) and SOC (two groups- 0.6-1.0 and 1.1-1.6 %). The data was analyzed using independent sample t-test. It was found that pH and CEC did not significantly affect soil B fraction. However, SOC had a significant effect on soil boron fraction viz., oxide bound and organic bound. In case of CS, majority of the soil properties viz., pH, soil organic carbon, available nitrogen, available phosphorus, cation exchange capacity, sand content (18.1- 49.5%) and silt content (24.1-48.4%) did not differ significantly among the cropping system. However, soil properties like available K2O content, EC, and clay (22.6-38.2%), was found to differ significantly between the cropping system. Cropping system did not significantly affect the various boron fractions in the present study. Significant positive correlation has been observed for soil organic carbon with Oxide bound B (r= 0.834**), Organically bound B (r= 0.541**), Specifically adsorbed B (r= 0.505*) and EC (r= 0.502*). A significant negative correlation has been observed in between sand and silt (r= -0.905 **) as well in sand and clay (r= -0.587**) content among the CS. The available boron (0.56 to 1.69 mg kg-1) and five boron fractions viz., Readily Soluble Boron (0.04-2.41 mg kg-1), Specifically Adsorbed Boron (0.15-1.92 mg kg-1), Oxide Bound Boron (5.18-17.41 mg kg-1), Organically Bound Boron (6.86-20.3 mg kg-1) and Residual Boron (17.73- 36.57 mg kg-1) did not differ significantly between the cropping systems. Results revealed that the relative proportion of various fraction of boron in soils are in the following order i.e. readily soluble B< Specifically adsorbed B < Oxide bound B< Organically bound B < Residual B. The Soil Quality Index for each CS were in the order: Rice-Rice (16.752)> Rice-Fallow (14.645)> Veg-Veg (12.979) > Plantation (12.742). None of the measured parameters were found to be significantly correlated with the yield of crop under the studied cropping system. The study, therefore explores the possibility of soil physico-chemical influence on soil boron fractions owing to cropping system over long period of time. The study reveals the selected soil properties influence on soil B fractions and cropping system being a non- determinant influencing any of the boron fraction studied.
  • ThesisItemOpen Access
    BIORESOURCE POTENTIAL OF FILAMENTOUS CYANOBACTERIA FROM PADDY FIELDS OF ASSAM AND ITS EVALUATION
    (AAU, Jorhat, 2021) Laishram, Nikita; Baruah, Rajen
    The present investigation was carried out to evaluate the bioresource potential of filamentous cyanobacteria from rice fields of Assam. Rhizospheric soil samples were collected randomly from Jorhat and Golaghat districts of rice rhizosphere. Altogether 77 cyanobacterial cultures were isolated from 55 numbers of soil samples using BGIIo specific liquid media and 30 cultures thus showed pure colonies. The 30 selected cultures were morphologically characterised on the basis of thallus morphology, trichome, vegetative cell structure, presence or absence of heterocysts and akinetes. The results showed that the cultures were non identical to each other and morphological data and microphotograph thus revealed probable genera belonging to Anabaena, Nostoc, Cylindrospermum and Calothrix. The soil nutrient status and soil enzyme assays as influenced by the various cyanobacteria indicated variation among the soil from where cultures were isolated. The correlation studies revealed a positive correlation with pH, organic C and enzyme activities. Also enzyme activities was seen to be positively correlated with available N, P, K. The nitrogenase enzyme activity was determined using ARA and results revealed a range of 7.70- 26.19 C2H2 nmol ml-1 hr-1 day-1 and culture BGA- 41 showed as the efficient culture. All the isolated cyanobacterial cultures produced significant amount of phytohormones with IAA, GA and cytokinin. Most of the cyanobacterial cultures exhibited positive results for siderophore production, HCN production and proteolytic activity. Quantitative activities of P solubilization and ammonia production was highest shown by BGA- 41. The cyanobacterial isolates were further screened for 16S rRNA gene sequencing for species identification and also to study the phylogenetic relationships among the cultures. The dominant cultures followed as Anabaena > Nostoc > Aliinostoc > Calothrix > Wollea> Cranbergia > Cylindrospermum. 10 efficient cultures based on enzyme and PGP activities were selected for pot experiment to study its efficiency in growth and yield attributing characters in rice crop variety Luit (Ahu). Results indicated that all the inoculated treatments showed better growth and yield as compared to the uninoculated control which was evident from the data obtained on number of tillers, number of panicles, length of panicles, grain yield (g/ hill), straw yield (g) and dry weight of root (g). Grain yield and straw yield of BGA- 41 ranged as 27.67 g/ pot and 12.64 g/ pot respectively. Therefore BGA- 41 was regarded superior to other cyanobacterial cultures which was at par with the recommended fertilizer dose treatment.
  • ThesisItemOpen Access
    INFLUENCE OF FERTILIZER MANAGEMENT PRACTICES ON POINT OF ZERO CHARGE (PZC) IN SOILS OF ASSAM AND ODISHA
    (AAU, Jorhat, 2021) Parija, Subhra; Nath Das, Kulendra
    An incubation study was undertaken to examine the influence of fertilizer management practices on the point of zero charge (PZC) in soils of Assam and Odisha. Six number of geo-referenced surface soil samples (0-15 cm) viz., black soil (Vertisol), laterite soil (Alfisol), red soil (Alfisol) and three alluvial soil samples belonging to Entisol, Inceptisol and Alfisol were collected from Kalahandi, Khordha and Dhenkanal districts of Odisha and Dergaon, Golaghat, ICR Farm AAU, Jorhat and Titabor, Jorhat of Assam, respectively. The soils strikingly varied in their mechanical composition, bulk density and moisture content at field capacity. The soils were mostly acidic in nature (pH 5.04 – 5.71) except black soil of Odisha which was slightly alkaline (pH 7.93). Organic carbon in Odisha soils ranged from 0.21 - 0.95% and lied between 0.47 - 0.86% in soils of Assam. All the soils were low to medium in available NPK but exhibited high content of available S. Laboratory incubation of these soils (200g) were carried out after treatment with four different fertilizer management practices viz., FYM @ 5 t ha-1 (T1), NPK @ 80:40:40 for Odisha soils and 60:20:40 for Assam soils (T2), FYM @ 5 t ha-1 + NPK @ 80:40:40 for Odisha soils and 60:20:40 for Assam soils (T3) and FYM @ 5 t ha-1 + NPK @ 80:40:40 for Odisha soils and 60:20:40 for Assam soils + Lime requirement/ Gypsum requirement (T4), in three replications. Sub samples were drawn after an interval of 15 and 30 days after treatment (DAT) and analysed. The PZSE and PZNC of the incubated samples were estimated through potentiometric titration and ion retention methods, respectively. Pearson’s correlation coefficient between PZC components and relevant soil properties was studied. The effect of the applied treatments on the PZC components and nutrient availability was evaluated using ANOVA for CRD. Results revealed that the PZSE for Odisha soils ranged from 2.18 to 4.70 and lied between 3.60 and 4.16 for the soils of Assam. The PZNC was achieved at comparatively lower pH values, ranging from 2.03 to 4.10 for Odisha soils and from 2.50 to 3.61 for Assam soils. The order of PZC for the samples was in direct correlation with their respective sesquioxide contents. Factors like clay, organic carbon, exchangeable calcium and available phosphorus imposed a significant influence on soil PZC values. The treatment T2 resulted in highest availability of the primary nutrients for all the soils under incubation while maximum availability of secondary nutrients was recorded under treatment T4. Availability of all the nutrients decreased at 30 DAT as compared to that of 15 DAT, except for Ca and Mg where the availability was more at 30 DAT. The treatment effect was insignificant on the sesquioxides content of incubated soils. Highest values of PZSE and PZNC were recorded under treatment T2 followed by T3, T4 and T1 for all the incubated soil samples of Odisha and Assam, however there was a decrease in the PZC values with increase in days of incubation. Such results confer that these soils allow more availability of anionic nutrients such as nitrate (NO3 -), phosphate (PO4 3-), sulphate (SO4 2-) immediately after fertilizer application, which slowly decreases with time favoring an increased CEC in the latter phase and thereafter enhancing the availability of cationic nutrients such as ammonium (NH4 +), potassium (K+), calcium (Ca2+), etc. In comparison to other treatments, the treatment T4 consisting of organic manures, recommended dose of chemical fertilizers along with lime/gypsum resulted as the most ideal fertilizer management practice. Besides providing optimum amount of primary nutrients and maximum amount of secondary nutrients, it regulated the PZC values favouring minimal loss of nutrients leading to enhanced crop production.
  • ThesisItemOpen Access
    INFLUENCE OF BIOCHAR ON SOIL PHYSICO-CHEMICAL PROPERTIES
    (AAU, Jorhat, 2021) Saikia, Priyambi; Patgiri, D K.
    The study on „Influence of biochar on soil physico-chemical properties‟ was conducted during 2019-2021 with the aim to characterize biochar obtained by pyrolysis of different organic sources, viz., ipomoea, rice straw and rice husk; and to study the influence of application of biochar on the physico-chemical properties of soils over a period of 90 days of incubation. Biochar was prepared by pyrolysis of organic sources under anaerobic condition at a temperature ranging from 350 to 400oC using the biochar kiln. pH, EC, CEC, available N, available P2O5, available K2O, water holding capacity (WHC) and bulk density of biochars ranged from 7.34 to 9.69, 0.70 to 1.13 dS m-1, 17.3 to 18.4 cmol(p+) kg-1, 0.0028 to 0.00504%, 0.0126% to 0.0258%, 0.17 to 0.34%, 101.58 to 255.36% and 0.267 to 0.465 Mg m-3 respectively. Soil samples of three different textural classes, viz., clay, clay loam and sandy were collected from the Titabor subdivision of Jorhat district for the incubation study. Soil samples were incubated for 90 days at 60% FC with each type of biochar (ipomoea, rice husk and rice straw) at 4 different levels (1, 2, 3 and 4%) in a completely randomized design. Biochar improved soil physical properties like hydraulic conductivity, soil water retention at field capacity, soil water retention at permanent wilting point, soil available water, increased sand and silt sized particles, while it decreased the clay sized particles compared to the initial value of the soils. Rice husk and rice straw biochar significantly decreased the percentage of clay sized particles (2.73%), by significantly increasing the percentage of sand and silt sized particles. All three soils showed a proportionate increment in sand and silt sized particles, while clay sized particles declined with the increase in the rate of application of biochar from 1 to 4%. When applied at a rate of 4%, rice husk biochar significantly increased the percentage of sand sized particles by its maximum value (2.25%) and rice straw biochar significantly increased the percentage of silt sized particles by its maximum value (2.42%). Application of rice husk biochar significantly improved hydraulic conductivity of the soils to the highest value (7.73 mm hr-1). Application of biochar derived from ipomoea led to significantly higher water retention at field capacity (28.10%), water retention at permanent wilting point (10.94%) and soil available water content (17.16%). Biochar showed corresponding increase in hydraulic conductivity till the application rate of 3% for clay loam and sandy clay loam soil. At the application rate of 3% rice husk biochar resulted for the highest hydraulic conductivity of the soil (9.11 mm hr-1). Soil water retention at field capacity and permanent wilting point increased proportionately with increase in the rate of application of biochar from 1% to 4% for all 32 soils except for sandy clay loam soil where soil water retention at field capacity proportionately decreased. Application of biochar at the rate of 3% and 4% significantly increased the soil available water content to the highest value (17.19%). Ipomoea at the rate of 4% led highest water retention at field capacity (29.91%) and soil available water (18.43%). Biochar significantly altered the soil pH, EC, CEC, organic carbon, available nitrogen, phosphorous and potassium content of the soils. Rice straw biochar led to significantly higher pH (5.88), EC (0.093 dS m-1) and organic carbon content (1.11%). Ipomoea biochar prompted significantly higher CEC [9.80 cmol(p+) kg-1], soil available nitrogen (251.38 kg ha-1) and available potassium content (311.41 kg ha-1). Rice husk biochar led to significantly higher available phosphorous content (72.69 kg ha-1). Soil chemical properties such as pH, EC, organic carbon, CEC, available phosphorous and potassium content was significantly increased with the increasing rate of application of biochar from 1 to 4%. Application of 4% rice straw biochar increased the soil pH, EC and soil organic carbon content to the highest level (6.39, 0.120 dS m-1 and 1.41% respectively). Ipomoea biochar at the rate of 4% led to highest CEC and soil available potassium content [11.07 cmol(p+) kg-1 and 358.59 kg ha-1 respectively]. Biochar made from rice husk at the rate of 4% increased the soil available phosphorous content to the highest level (96.06 kg ha-1). However, application of biochar till 2% resulted in increase in available nitrogen content of the soils. Further increase in application rate resulted in decrease in available nitrogen content of the soils. Ipomoea biochar at the rate of 2% increased the soil available nitrogen content to the highest level (271.71 kg ha-1).
  • ThesisItemOpen Access
    HYDROPHYSICAL PROPERTIES AND ERODIBILITY OF BRAHMAPUTRA RIVER BANK SOILS UNDER GOLAGHAT DISTRICT
    (AAU, Jorhat, 2021) GOSWAMI, DIPSIKHA; Deka, Bipul
    The study on the hydrophysical properties and erodibility of Brahmaputra river bank soils under Golaghat district was carried out with the objectives 1) To assess hydrophysical and chemical properties of soils along the bank of Brahmaputra river and 2) To estimate soil erodibility indices of the studied soils. The studied area is located in the Golaghat district which is a part of Upper Brahmaputra Valley Zone of Assam. It encompasses an area of 195.52 sq. km and lies between 93°71' E to 93°99' E longitude and 26°67' N to 26°80' N latitude and with an elevation ranging from 79 to 84 m. Thirty eight surface soil samples (0-15 cm) both disturbed and core were collected using handheld GPS of Garmin Etrex 20 upto 5 km from the bank of Brahmaputra river towards southern direction. The sampling sites were demarcated across the flow of Brahmaputra river traversing a total distance of 25-30 km from East to West. The surface as well as core samples were analysed for various hydrological and chemical properties following the standard procedures. The studied soils exhibited soil texture ranging from loamy sand to silty clay loam, however, silt loam was the dominant one. The amount of silt and clay content were found to be somewhat higher than sand content in the areas away from the river bank and reverse trend persisted in case of total sand content. The bulk density, particle density of investigated soils ranged from 1.22 to 1.59 Mg m-3 with a mean value of 1.37 Mg m-3 and 2.31 to 2.65 Mg m-3 with a mean value of 2.47 Mg m-3 respectively. The porosity of the studied soils ranged between 32.63 to 49.03 per cent, while the hydraulic conductivity ranged between 0.29 to 1.34cm hr-1 . The water holding capacity ranged from 21.45 to 45.01 per cent while the field capacity, permanent wilting point and available water content values varied from 17.78 to 33.12 per cent, 4.45 to 13.03 per cent and 6.26 to 24.02 per cent respectively. The studied soils showed significant positive correlation of water holding capacity, field capacity with clay which exhibited that dominance of finer particles increases the capillary pores and maximum surface area to hold water. Hydraulic conductivity showed significant negative correlation with clay and exhibited high values of hydraulic conductivity in the soils where clay content is low or finer materials being migrated due to erosion. The macro aggregates, micro aggregates and mean weight diameter of the studied soils varied from 41.93 to 84.07, 15.93 to 58.07 per cent and 0.72 to 3.88 mm, respectively. The studied soils were acidic in nature and the pH of the soils ranged between extremely acidic (4.45) to slightly acidic (6.74) with a mean value of 5.56. The organic matter of the studied soil area varied from 0.94 to 2.62 per cent with a mean of 1.77 per cent. The mean values of available nitrogen, available phosphorus, available potassium content of soils were 288.42, 44.37, 84.71 kg ha-1 respectively and their status ranged from low to medium. On the basis of the estimated values of soil physico-chemical properties, various soil erodibility indices were computed. The silt/clay ratio, clay ratio and modified clay ratio in the studied soils ranged from 0.75 to 2.43, 1.30 to 7.36 and 1.23 to 6.79, respectively. Among the dispersion ratio, erosion ratio and erosion index, dispersion ratio ranged from 0.05 to 0.33 with a mean of 0.17, erosion ratio ranged from 0.03 to 0.18 with a mean of 0.08 and erosion index ranged from 0.03 to 0.32 with a mean of 0.10 respectively. EIROM values ranged from 0.60 to 3.96 with a mean of 1.15 and it exhibited similar trend like EI as showed significant positive correlation with very fine sand and significant negative correlation with clay content. The values of soil erodibility factor in the studied soils ranged from 0.09 to 0.12 with a mean of 0.10. GIS based schematic mapping revealed that among the physical properties total sand covered highest area nearly 134.64 sq. km (68.86 per cent) of the studied area in the range of total sand content less than 25 per cent. Silt content range 40-50 per cent covered the highest area nearly 137.80 sq. km (70.48 per cent) of the studied area which were away from the river bank. Clay content exhibited highest area nearly 109.86 sq. km (56.18 per cent) in the clay content range of 30-35 per cent and among the hydraulic properties , available water content covered highest area i.e 116.55 sq km (59.61 per cent) in the range of 15-20 per cent, hydraulic conductivity range 0.5-0.75 cm hr-1 covered highest area nearly, 123.70 sq km (63.27 per cent), field capacity values in the range of 20-25 per cent covered highest area i.e 116.55 sq km (59.61 per cent) of the studied soil area. Water holding capacity values in the range of 35-40 per cent covered highest area i.e 116.55 sq km (59.61 per cent) of the studied soil area. Macroaggregates recorded highest area nearly 147.09 sq. km (75.23 per cent) of the studied area in the macroaggregate content range 75-80 per cent. Nearly 3.9 sq. km (2 per cent) of the studied area had dispersion ratio value more than 0.15 which could be considered as erodible. About 12.05 sq. km (6.16 per cent) of the studied area had erosion ratio values more than 0.10 indicating their susceptibility to erosion. The erosion index values were more than 0.15 in about 3.9 sq. km (2 per cent) of the studied area.
  • ThesisItemOpen Access
    BIOCONVERSION OF MUNICIPAL SOLID WASTE INTO FORTIFIED COMPOST USING MICROBIAL MEDIATORS
    (AAU, Jorhat, 2021) Bora, Rimjim Sikha; Gayan, Anjuma
    Rapid composting of municipal solid waste (MSW) collected from two different sites(main landfill of Jorhat municipal corporation and dumping site of Rowriah, Jorhat,Assam), was done using three different decomposers microbial consortiagroup (DMC @1%) for 60 days, and thereafter biofortification of the MSW compost was done by addition of plant growth promoting rhizobacteria (PGPR) for 20 days.The DMCgroup were previously isolated from polluted sites of Assam, and denominated as paper group, oil group and cement group. For comparison with MSW, agro-waste was also used in the study, which did not receive DMC, but received PGPR application after 60 days.At 80 DAI (days after inoculation),pHwas stabilized in the range between 7.40-7.76 in MSW I and 7.00-7.55 in MSW II, electrical conductivity (EC) was recorded to be in the range3.08-5.21 dS m-1(MSW I) and 1.55-3.85 dS m-1(MSW II).The temperatures during composting period were maintained between 27.33-28.66°C in MSW I and 28.66-32.33°C in MSW II, while the moisture content decreased in both sites at 80 DAI. Following PGPR application, total carbon content declined to a minimum of 17.24-24.82% in MSW I and 17.52-27.7% in MSW II, while total nitrogen content increased to 1.01-1.7% in MSW I and 0.85-1.53% in MSW II. Total phosphorus and total potassium content also exhibited increasing trend till the end of composting.At 80 DAI, C:N ratio declined over uninoculated treatment in both sites and ranged between10.37-15.90 (T1-T3) in MSW I and 12.26-13.13(T1-T3) in MSW II,.NO3-N elevated till the end of composting, contrarily, NH4+-Ndeclined to a minimum of 0.09-0.27% in MSW I and 0.08-0.27% in MSW II.CEC increased to 22.35-29.99 c mol (p+) kg-1 in MSW I and 22.43-28.17% c mol (p+) kg-1 in MSW II. Heavy metals, viz- Pb and Cdcontent decreased to 98.20-250 ppm(T1-T3) and 0.74-0.81ppm(T1-T3) during PGPR fortification.Total bacterial count of the fortified compost was displayed at 6.17 to 7.01Log cfu g-1in MSW I and 6.16 to 6.93 Logcfu g-1in MSW II, while fungi population recorded at 4.81 to 6.03 Log cfu g-1 in MSW I and 4.91 to 6.06Log cfu g-1 in MSW II. Actinomycetes population recorded at 6.70 to 6.99 Log cfu g-1in MSW I and 6.68 to 7.00 Log cfu g-1in MSW II at 80 DAI.Estimation of biologically important enzymes (phosphomonoesterase,dehydrogenase, arylsulphatase, and fluorescein diacetate hydrolysis) provided information on the rate of organic matter degradation following inoculation with DMC and PGPR biofortification. Upon addition of PGPR, microbial biomass carbon (MBC) attained a range of higher values in between 210.66-1167.21 μg g-1 in MSW I and 201.46-1005.6 μg g-1in MSW II. Overall gradual drop of basal respiration rate and increment in microbial quotient was observed after addition of PGPR to MSW compost. A pot culture experiment was designed to check the efficacy of test plant Soyabean which exhibited that the MSW compost produced was non-toxic and displayed significant difference between the DMC treated plants over the uninoculated control. Study revealed that microbial mediators (DMC and PGPR) used during composting are efficient and can result in better bioconversion of MSW to usable compost.
  • ThesisItemOpen Access
    Assessment of Soil Zinc Fractions and their Relationship with Physico-Chemical Properties of Rice Growing Soils of Boko Block of Kamrup(rural) District, Assam
    (AAU, Jorhat, 2021) Kalita, Abreeta; Borkakati, Kabindra
    A study on ‘Assessment of Soil Zinc Fractions and their Relationship with Physico-Chemical Properties of Rice Growing Soils of Boko Block of Kamrup(rural) District, Assam’ was conducted during 2019-2021 with the objectives to assess different zinc fractions along with the physical and chemical properties of three rice growing soils namely Ahu, Sali and Boro rice. The texture of the soils varied from sandy loam to clay loam for Ahu and Sali rice while clay loam in Boro rice growing soils with strongly acidic to moderately acidic in their reactions (pH 4.52 to 5.85). Soil organic carbon was medium to high in Ahu and Sali rice but high in Boro rice growing soils. All the available primary nutrients were medium in their status except available phosphorus which was low to medium. Significant negative correlations were recorded among soil pH, EC and SOC, and among sand, silt and clay fractions while significant positive correlation was observed between SOC with CEC, available nitrogen, clay and CEC with available nitrogen, potassium, exchangeable calcium, magnesium and clay and available nitrogen with clay and exchangeable calcium with exchangeable magnesium. The distribution of Zn-fractions followed a general order of dominance as WSEX-Zn