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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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ThesisItem Open Access VARIABILITY OF GROUND WATER RECHARGE CHARACTERISTICS AND QUALITY IN JORHAT DISTRICT, ASSAM(AAU, Jorhat, 2019-07) Saikia, Mridupawan; Patgiri, D. K.The present investigation was carried out in Jorhat District aimed at assessment of the groundwater, its recharge characteristics and quality. The district spread from 93o58’32” to 94o36’24”E longitude and 26o20’51” to 26o56’29” N latitude. Soil and water samples were collected from 265 randomly selected GPS enabled locations of Jorhat district at an interval of around 4-5 km. Representative soil and water samples were collected from each location (both disturbed and core sample) from two depths viz. 0-30 and 30-60 cm. Depth of groundwater in each location were recorded during the months of January, April, July and October in 2017 and 2018 as well. Thematic maps were prepared using the GIS software TNTMips. Geostatistical parameters were computed following standard methods. The bulk density and particle density ranged from 1.16-1.59 and 2.24-2.65 mg/m3 in 0-30 cm depth and 1.19-1.61 and 2.28-2.68 mg/m3 in 30-60 cm depth. The bulk density of the soil showed negative significant correlation with porosity and water content at 0.1 to 15 bar matric suction in both the depths.The Organic carbon content 0-30 cm depth ranged from 0.87-1.86 per cent while at 30-60 cm depth it ranged from 0.38-1.21 per cent. The soil pH in both the depths were acidic and ranged from 4.50-6.60 and 4.23-6.84 at 0-30 and 30-60 cm depth, respectively.The texture of the soils ranged from heavy towards the higher elevation to light towards the lower elevation areas.The Porosity and Saturation water content ranged from 33.47-53.28 and 19.87-43.19 per cent in 0-30 cm depth and 34.76-53.28 and 19.73-42.34 per cent in 30-60 cm depth respectively. Porosity showed significant positive correlation with organic carbon and clay and negative significant correlation with sand. With increase in matric suction of the soil from 0.1 bar to 15 bar the water content of the soil decreased.The pore interaction (b) parameter ranged from 2.03-3.56 in 0-30 cm depth and 1.94-3.96 in 30-60 cm depth. The mean saturated hydraulic conductivity of the soils for the two depths were 1.01 and 0.65, respectively, indicating higher saturated hydraulic conductivity at surface as compared to sub-surface soil. Saturated hydraulic conductivity showed positive correlation with sand and negative correlation with clay. Ground water table depth during January and April were very low, while it reached surface during July and October for both 2017 and 2018. Groundwater depth during all the months during 2017 showed mixed correlation with physico-chemical properties.Thematic maps revealed the pattern of groundwater movement in different range.The decline during first quarter in both the years indicated wide ranging variability.Thus, it is quite obvious that the soil properties associated with transport of water both in saturated and unsaturated condition favoured transport of water.The groundwater table during the quarter July to October, 2017 and 2018 indicated that in some of the areas, the same did not decline at all and were at surface. The rate of decline of groundwater table becomes faster with the arrival of the dry season for which during the quarter from October, 2017 to January, 2018 groundwater table declined from 64.00 to 139.00cm. During the quarter from January to April, 2018 decline in groundwater table indicated that although there were general decline, the same was less than that of the corresponding quarter in the previous year. This maybe due to the fact that the region received some amount of rainfall during the quarter and the entire quantity may have helped reduce the rate of decline of groundwater in 2018.The region received pre-monsoon shower during the months of April and May and the groundwater table during the quarter from April to July, 2018 rose from 82.00 to 220.00 cm. This rise is considerable considering the fact that the average rise was 170.30 cm indicating that whatever the rainfall is received, the same had invariably gone down the profile and recharged it. Thus, it made up for the decline of groundwater table during the previous months. The pH, zinc, calcium, magnesium, fluoride, aluminium and boron content of groundwater of the district are all within permissible limit set by WHO. However, iron and arsenic content in groundwater are far beyond permissible limit set by WHOand need some treatment to make it potable. The semivariogram parameters for depth of groundwater in Jorhat District during the period of study reveals that the trend of nugget and sill variance followed the trend of fluctuation of depth of groundwater table during the period of study. The nugget/sill ratio revealed that in almost all the months the variability was medium to high. Data on semivariogram parameters for the different quality parameters for groundwater revealed that Arsenic and Chloride showed the lowest and highest nugget and sill, respectively. The ratio of MAE, MRE and RMSE between kriging and IDW revealed that the ratios were more than 1, indicating that kriging estimated these parameters higher than that of Inverse distance weighting (IDW). Thus, this indicated that IDW was a better method of interpolation for these parameters. IDW method of interpolation improvised the maps from 0.93 to 12.25 per cent.ThesisItem Open Access NITROGEN DYNAMICS IN A RICE-RICE SYSTEM OF UPPER BRAHMAPUTRA VALLEY ZONE (UBVZ) OF ASSAM(AAU, Jorhat, 2019-05) Tamuli, Babita; Bhattacharyya, DevajitThe study investigated mineral N and labile soil organic N dynamics at different growth stages of rice and their distribution within soil depth (0-80 cm) under various combinations of inorganic and organic fertilization in a rice-rice cropping system of UBVZ of Assam. Further partial balance of mineral N and total N stock of the soils were determined. The study was conducted in a long term fertility experiment at Regional Agricultural Research Station (RARS), Assam Agricultural University, Titabar, Jorhat in 2017 taking the selected treatments viz., Control, 100% NPK, 100% NPK + FYM 5t/ha, 50% NPK, 50% NPK+ 50% (FYM) N and FYM 10t/ha for rabi and kharif rice cropping sequence. Soil samples were collected from different depth (0-20, 20-40, 40-60 and 60-80 cm) before transplanting of rabi rice, at active tillering, flowering and physiological maturity stages of rabi and kharif rice and after harvest of kharif rice. Physiochemical properties analysed in the soils collected before transplanting of rabi rice of 2017 was considered as initial. Soil samples of three growth stages of rabi and kharif rice were analysed for mineral and labile soil organic N. Straw and grain samples collected at harvest of rabi and kharif rice were analysed for their N concentration and N uptake. Partial balance of soil mineral N in surface soils (0-20 cm) and total N stock within 0-80 cm soil depth was estimated at the end of the cropping sequence. The pH of the soils was higher in treatments FYM 10t/ha (5.87), 100% NPK+ FYM 5t/ha (5.72) and 50% NPK+ 50% (FYM) N (5.67) than the control (5.33) but was significantly lower in treatments 100% NPK (5.13) and 50% NPK (5.25). Soil organic carbon (OC) content had built up significantly in all the treatments compared to control. Organic carbon decreased significantly with increased soil depth. The bulk density (BD) of the soils varied from 1.18 (FYM 10t/ha) to 1.36 g cm−3 (control). The highest total and mineral N before transplanting of rabi rice and after harvest of kharif rice was recorded in 100% NPK+ FYM 5t/ha which was significantly higher over rest of the treatments. In the study of mineral N dynamics, NO3-N and NH4-N were found to be significantly higher in 100% NPK+FYM 5t/ha fertilized plots at the three growth stages in both rabi and kharif rice. The higher NO3-N at active tillering stage was 12.73 and 11.53 mg kg-1 in rabi and kharif rice, respectively, in 100% NPK+FYM 5t/ha fertilization, which gradually decreased at physiological maturity stages of both the rice season (10.70 mg kg-1 in rabi and 9.94 mg kg-1 in kharif). Similar decreasing trend was also observed in NH4-N from active tillering (10.67-17.59 mg kg-1 in rabi and 8.67-16.67 mg kg-1 in kharif) to physiological maturity stages (9.22-16.53 mg kg-1 in rabi and 6.76-14.39 mg kg-1 in kharif). Both NH4-N and NO3 -N showed a distinct decreasing trend with increase in soil depth. The significantly the highest grain (4.66 and 5.54 t ha−1 ) and straw (6.58 and 6.64 t ha−1 ) yield of rabi and kharif rice and total N uptake were observed in 100% NPK+ FYM 5t/ha treated plots. However, this grain yield was statistically at par with yield in treatments 100% NPK at rabi and FYM 10t/ha and 100% NPK in kharif rice. The soil partial mineral N balance revealed that with application of inorganic fertilizer (100% NPK and 50% NPK) and with no fertilizer application (control) resulted in a negative partial soil N balance. However, application different combinations of organic FYM and inorganic NPK fertilizers as well as 10t/ha FYM alone had lead to positive N balance in soils as well as higher N stock. The highest N balance (18.74 kg ha-1) and N stock (1.51 Mg ha-1) was found in application of 100% NPK + FYM 5t/ha followed by that in application of FYM 10t/ha (3.63 kg ha-1 and 1.33 Mg ha-1, respectively). The labile soil organic N fractions of the soils viz., microbial biomass N (MBN), particulate organic N (PON) and water extractable organic N (WEON) was decreasing with increase in crop growth from active tillering to physiological maturity stage. The decrease in MBN, PON and WEON in rabi varied from 10.85-16.85 to 9.65-16.03 mg kg-1, 0.21-0.89 to 0.14-0.68 g kg−1 and 6.64-12.43 to 5.31-10.68 mg kg-1, respectively; and in kharif from 8.45-13.04 to 7.28-12.0 mg kg-1, 0.16-0.57 to 0.1-0.48 g kg−1, 4.87-9.49 to 3.48-7.95 mg kg-1, respectively.The labile soil organic N fractions were significantly higher in FYM 10t/ha treated plots which might be due to creation of suitable conditions for microbial growth by FYM. All the labile fractions of soil organic N decreased significantly with increase in soil depth. This might be due to decrease of OC with soil depth. The N fractions of the soils viz., NO3-N, NH4-N, MBN, PON and WEON showed a significant positive correlation with soil OC and total N content at the three growth stages in rabi and kharif season. Multiple regression analysis of grain yield with various fractions of N showed that NH4-N (R2=0.745) was the main contributor to the grain yield at early growth stage of rabi rice. Whereas, WEON (R2=0.901) was the main contributor to the grain yield in kharif rice. The results of the investigation indicated that the NH4-N and NO3-N were the main contributor to the total uptake of N at three different growth stages in both the rice season. All the fractions of N were significantly and positively correlated with each other (p<0.01). Most of the N mineralized in the soil was expected to occur in the labile N fractions. The positive correlation observed between labile N fractions and mineral N also supported their close interrelation. The multiple regression analysis of various N fractions with total N stock indicated that NH4-N was the main contributor to the N stock of the studied soils under rice-rice cropping system. The present investigation leads to the conclusion that combined applications of 5 t/ha FYM with 100% NPK at present could be considered as the best nutrient management practices in rice-rice system of UBVZ of Assam in terms of the highest yield, N balance, N stock and sustainable soil health (pH, OC and BD). Moreover, the treatment of organic nutrient management 10t FYM/ha could also produce rice yield statistically at par with 100% NPK + FYM 5t/ha, had positive N balance and was the best treatment for sustainable soil health. Therefore, better organic nutrient management which could produce higher yield than 10t FYM/ha might be the present requirement for the rice-rice system of the UBVZ of Assam.ThesisItem Open Access ASSESSMENT OF CARBON FOOTPRINT IN RICE-RICE CROPPING SYSTEM AS AFFECTED BY FERTILIZER MANAGEMENT(AAU, Jorhat, 2019-07) Borah, Rupjyoti; D, K.N.The present study aimed at assessing the carbon footprint in rice-rice cropping system as affected by various fertilizer management combinations and source of nitrogen was carried out in the ICR Farm, AAU (26°71'N, 94°18' E) 91.0 m above MSL during the years 2016-17 and 2017-18. The initial pH, organic carbon, available N, P2O5 and K2O of the experimental plot were 5.84, 0.61%, 132.561 kg ha-1, 214.48 kg ha-1 and 33.734 kg ha-1, respectively. There were no significant differences in soil pH amongst the variety while significant differences were observed within various fertilizer combinations and source of N. Soil organic carbon values ranged between 0.62 to 0.85% and significant difference was observed amongst the fertilizer treatments and source of N. The various fertilizer combinations in case of available nitrogen also showed a similar trend with the highest mean value of 169.84 kg Nha-1 in the treatment with full recommended dose of fertilizer (RDF). Available P2O5 in the system also followed a similar trend (36.07 kg ha-1) while available K2O significantly varied within the varieties and fertilizer combinations with higher values in Mahsuri-Banglami system (49.94 kg K2O ha-1). Significant differences in methane emissions were observed amongst the varieties and also in between the fertilizer combination treatments.The methane emission was 388.33 mg m-2hr-1 in Ranjit-Lachit system and 285.61 mgm-2hr-1 in the Mahsuri-Banglami cropping system. High methane emission was observed in RDF followed by 50% RDF+Vermicompost and INM. During the entire crop growing season, the largest variation in methane emission was observed in the early growth period. Methane emission indicated two distinct peaks during the entire crop growth period, irrespective of the treatments. Peaks of nitrous oxide emissions were obtained after topdressing of nitrogenous fertilizers. Significant variations were also observed in between the fertilizer combination treatments may be due to varying organic carbon in the various treatments. Ranjit-Lachit system recorded higher mean cumulative N2O emissions (10.72 gm-2) than Mahsuri-Banglami system (4.92 gm-2). The RDF treatments recorded highest mean cumulative N2O emissions amongst the fertilizer combinations. Temporal pattern of flux irrespective of treatments showed a trend of gradual increase with the growth of the crop, thereafter a slow decline in fluxes. The highest mean cumulative CO2 emissions (2953.43 mg m-2) was recorded in the Ranjit-Lachit system and within the fertilizer combinations, the highest mean value of 3125.20 mg m-2 was recorded under RDF treatment. Mapping of the three different tiers of carbon footprint showed that the tier-1 was the dominant contributor of carbon footprint. The Total System Spatial Carbon Footprint (SCF) under different treatments recorded higher values in case of INM treatments involving 50%NP + Full K + 5t/ha enriched compost and vermicompost treatments in both the cropping systems. Within the INM treatments, higher SCF of 62.00 t CE ha-1 was obtained in Ranjit-Lachit system while in case of Mahsuri-Banglami system, the highest SCF was obtained in INM treatment with NCU and UCU (48.91 t CE ha-1). Yield scaled carbon footprint (YCF) indicated highest value of 13.23 kg CE kg-1 grain in case of Mahsuri-Banglami system while 50% RDF supplemented with 5 t ha-1vermicompost and uncoated urea recorded the highest YCF with 15.96 kg CE kg-1 of grain in Ranjit-Lachit cropping system. Considering the yield compensation and sustainability of the soil resources, the INM with slow release N source proved to be the better in rice-rice cropping system.ThesisItem Open Access CHANGES IN SOIL BIOLOGICAL PARAMETERS AS EFFECTED BY THE APPLICATION OF ORGANIC INPUTS IN RICE-TORIA SEQUENCE(AAU, Jorhat, 2019-07) Chauhan, Manoj Kumar; Baruah, RajenThe field trials were conducted to assess the changes in soil chemical and biological parameters along with yield and yield attributing characters of rice and toria crops in sequence during 2015-17. The treatment combinations were as Control (T1), 50% recommended dose of fertilizer (RDF)+50% biofertilzer (BF) (T2), 50% RDF+50% Enriched Compost (EC) (T3), 100% RDF (T4), 100% BF (T5) and 100% EC (T6). The data were recorded at various stages of crop growth and soil samples were analysed for different characters at different stages of rice and toria crops. The results showed that the treatment T3 consisting of 50% EC and 50% RDF recorded the highest accumulation of N (265.49 and 258.01 kg/ha), P (23.14 and 23.00 kg/ha), and K (152.94 and 148.38 kg/ha) at maximum tillering stage of rice and flowering stage of toria, respectively but remained at par with 100% RDF treatment in both the crops during the period of investigations. The accumulation of organic carbon (12.49 g/kg soil in rice and 12.14 g/kg soil in toria) was recorded significantly higher than 100% RDF treatment (11.01 g/kg soil in rice and 10.60 g/kg soil in toria) at similar stages of both the crops which remained at par with 100% EC (T6) treatment. Soil accumulation of Organic carbon (OC), N, P and K was found higher in T6 treatment over T5 treatment. However, soil accumulation of OC, N, P and K gradually declined from maximum tillering stages of rice and flowering stage of toria to harvesting stage of both the crops. Although no significant changes in soil pH was recorded, but the lowest pH was recorded in T4 treatment in both the crops ranging from pH 5.19 to pH 5.22, even lower than the initial soil pH value of 5.24. The results revealed that the bacterial, fungal and actinomycetes population varied with the treatments and with the stage of the crops. The treatments comprising of 50% EC and 50% RDF (T3) recorded the highest bacterial population of 19.63 cfu x105/g and 19.25 cfu x105/g soil at flowering stages of rice and toria, respectively. The fungal population was 9.12 cfu x105/g soil in rice and 8.88 cfu x105/g soil in toria, respectively. The actinomycetes population was 45.75 cfu x104/g soil in rice and 45.12 cfu x104/g soil in toria at flowering stages of rice and toria crops and declined thereafter at harvesting stages of both the crops. The microbial diversity in T3 and other organic treatments found significantly higher than 100% RDF and control treatment. Soil respiration, microbial biomass carbon, and soil enzymes (fluorescein di-acetate activity, dehydrogenase activity, acid phosphatase activity and urease activity) behaved differently with different treatment whereas T3 (50% EC + 50% RDF) exhibited the best performance over other treatments at all the stages of rice and toria crops during both the years. All the biological parameters were found at their peak at flowering stages and declined thereafter at harvesting stages of both the crops. All the bio-chemical properties in treated plots in rice-toria sequence were found significantly higher than the untreated control and even over the initial values of each parameters. Unlike soil bio-chemical properties, agronomic parameters of rice (no. of tillers/hill, plant height, panicle length, grain and straw yield) and toria (plant height, no. of siliqua/plant, grain and stover yield) crops recorded higher values in 100% RDF (T4) treatment which remained at par with, 50% EC + 50% RDF treatment (T3). The grain yield of rice (45.09 q/ha) and toria (893.38 kg/ha) in the 100% fertilized plots (T4) were found at par with T3 treatment (43.72 q/ha in rice 885.63 kg/ha in toria) receiving 50% EC and 50% RDF, but both recorded significantly higher yield over sole application of biofertilizer, enriched compost and control treatment. The beneficial effect of INM treatment (T3) that facilitated favourable soil conditions were reflected in grain yield of both rice and toria crops which was equivalent even with 100% RDF treatments. Rice yield was more closely and positively correlated (at p<0.05) with OC (r=0.587*), N (r=0.932*), P (r=0.746*) and K (r=0.972*) as compared to soil enzymes such as acid phosphatase (r=0.637*), urease (r=0.512*). Similarly, a strong relationship was also recorded among toria yield with OC, N, P and K and other soil biochemical properties. Furthermore, soil respiration and MBC exhibited strong relationship both in rice (r=0.961*) and toria (r=0.966*) crop. All the soil biological properties registered positive correlation with chemical properties of soil.ThesisItem Open Access EFFECT OF CRUDE OIL SPILLAGE ON SOIL PHYSICAL PROPERTIES AND RECLAMATION OF THE AFFECTED SOILS(AAU, Jorhat, 2017-07) Goswami, Kasturi; Kulendra Nath DasThe release of crude oil into the environment by oil spillage is receiving worldwide attention due to the potential risk posed to the environment. Crude oil spillage is a regular phenomena in the oil drilling sites and the areas through which oil transportation pipelines carries the crude oil either to the oil collecting station (OCS) or to the oil refineries. Due to raining and flooding the spilled oil and oily sludge spread to the nearby cultivated field causing soil pollution and heavy reduction in the crop yield. Therefore, the present investigation was aimed to study the effect of crude oil spillage on soil physical properties and the influence of organic amendments as remediants in reclaiming the affected soils. Five soil samples in triplicates at an interval of 50m from three directions (E,W& S) from the spilled areas and one samples each from adjacent unpolluted areas were collected from two oil fields of Assam i.e. MFN, Moran, Dibrugarh and HYR, Kathalguri, Duliajan, Tinsukia where oil exploration activities are conducted by Oil India Limited (OIL). The samples were characterized for their physico-chemical properties. A pot experiment was conducted in the Department of Soil Science, AAU, Jorhat, Assam with unpolluted soils from the above oil fields under factorial set of treatments having five levels of crude oil pollution (0, 60, 90, 120 and 150 ml) and seven amendment treatments viz. poultry manure (PM), farm yard manure (FYM), vermicompost (VC), poultry manure + farm yard manure (PM + FYM), poultry manure + vermicompost (PM + VC) and farm yard manure + vermicompost (FYM+VC) with one control. After 30 days of crude oil addition, the soils were treated for another 15 days with the amendments, and then rice seedling of var. Ranjit was transplanted and grown upto the harvest of crop for two consecutive years i.e. 2014-15 and 2015-16 repeating treatments in 2nd year. Soil samples were collected before crude oil application, after 30 days of pollution treatment, after 15 days of amendment treatment and after harvest and analyzed for their physico-chemical properties. All agronomical data were recorded after harvest of the crop. The results revealed that the soils of Moran and Duliajan oil fields at 0m distance were highly affected by the oil spillage. The bulk density of soils increased from 1.31 to 1.63 Mg m-3 and 1.25 to 1.62 Mg m-3 in Moran and Duliajan oil field respectively, while decreased the total porosity, water holding capacity and hydraulic conductivity. The pH of the soil remarkably dropped with decrease in distance from 5.40 to 4.91 and 5.45 to 4.92, respectively making the soil strongly acidic in nature whereas the organic carbon content increased from 7.12 to 27.36 g kg-1 in Moran and 7.39 to 26.35 g kg-1 in Duliajan oil field. The available N and P2O5 were low near the spillage point and substantially increased with distance. Conversely, Av-K2O, exchangeable Ca2+ and Mg2+ significantly increased near the spilled point. The mean weight diameter (MWD) was maximum near the spillage point and decreased with increasing distance. The water stable aggregates (WSAs) were found higher in the coarser fraction (> 5mm) in soils of 0m and 50m distance whereas beyond 50m, finer fractions recorded the maximum WSAs. Similar trend was observed in organic carbon content in various fractions of WSAs. The total petroleum hydrocarbon (TPH) was maximum at 0m distance in both Moran (14.48 mg g-1) and Duliajan (11.59 mg g-1) oil fields and was negligible beyond 200m. Water retention capacity of soil was lowest at all the applied pressures in the vicinity of drilling point while the values increased with distance. The results of the pot experiment revealed that addition of pollutant deteriorated the soil physico-chemical properties by increasing bulk density of soils while decreasing porosity and water holding capacity. The soil became more acidic and organic carbon and TPH content of soils increased with increased pollution levels whereas the available N, P2O5, K2O and exchangeable Ca2+ and Mg2+ decreased significantly. The addition of organic amendments considerably improved soil parameters by decreasing soil bulk density and TPH content and increasing pH and available nutrient and exchangeable cations. The PM+VC combination amendment showed better results at all the pollution levels. Increase in pollution levels significantly and adversely affected yield attributing characters more pronouncedly at 150ml of crude oil. Addition of different amendment treatments improved the aforesaid plant characters with significant increase in grain and straw yield. The present investigation reveals crude oil spillage as a major factor of soil quality deterioration in Moran and Duliajan oil fields of Assam and the impact was more pronounced in the vicinity of drilling point adversely affecting all the physico-chemical properties of soil. Addition of different levels of crude oil as pollutant also established unfavourable affect on physical properties of soil such as bulk density, particle density, porosity, water holding capacity etc. along with the chemical properties and nutritional status of the soil. Application of organic amendments in various combinations observed to improve soil physico-chemical properties specially reducing TPH content of the soil. Organic amendments i.e. poultry manure + vermicompost (PM+VC) exhibited its excellent capacity to reduce pollution level implying their potentiality as a promising bioremediant for reclamation of crude oil polluted soils. Further, this combination proved to be superior in maintaining crop yield and soil quality.ThesisItem Open Access GIS-BASED EVALUATION OF WATER QUALITY INDEX OF GROUNDWATER AND IDENTIFICATION OF ARSENIC VULNERABLE ZONE FOR POSSIBLE MITIGATION IN RICE ECOSYSTEM OF NAGAON DISTRICT, ASSAM(AAU, Jorhat, 2017-07) Thakuria, Imdad Hussain; Medhi, B. K.Water Quality Index (WQI), a technique of ranking water quality, is an effective way to assess quality and ensure sustainable safe use of water. The present work is aimed to assess groundwater arsenic along with the status of other parameters, their distributions, establishing relationship and evidently finding low cost less arsenic loading technology in irrigated rice field of Nagaon district of Assam for understanding the suitability of water by calculating the WQIand Geographical Information System (GIS) techniques. Eight hundred and eighty three groundwater samples were collected during post-monsoon, 2014-15 and 2015-16 for comprehensive water quality analysis. The spatial distribution maps of 14 decisive parameters viz., arsenic, pH, electrical conductivity, total dissolved solids, calcium, magnesium, carbonate, bi-carbonate, nitrate, sulphate, fluoride, iron, aluminium and manganese having desirable and undesirable classes based on BIS and WHO standards were prepared using Arc GIS 9.3 software. The results of spatial variability maps to identify vulnerable risk zone of different groundwater quality parameters indicated an increase in the percentages of contamination levels especially for arsenic (40.4% – 99.5%), aluminium (99.8%), iron (89.6) and manganese (73.5%). Total Dissolved Solids, calcium, magnesium, carbonate, bi-carbonate, nitrate sulphate and fluoride were recorded within the desirable limit and considered to be safe. The concentration of Fluoride in certain areas (33 per cent) of the district was found far below the lower threshold limit suggesting the concerned agencies to opt for suitable less fluoride management strategies. The overall Water Quality Index was found to be 96.48 distinguishing the ground water as “GOOD WATER” with a tendency to fall in “POOR WATER” category. Spatial autocorrelation for all the quality parameters were found distributing in three patterns viz. CLUSTER for pH, EC, As, F, Fe, Al, Mn,HCO3; RANDOM for Mg, Ca, CO3, NO3, SO4 and DISPERSED for TDS, and thus paving a way to address these important parameters based on their space and values. Relationship between groundwater as well as soil arsenic content with other quality parameters showed that 39.1% of arsenic in ground water and 10.4% arsenic in soil could be predicted by the above mentioned parameters.In regards to arsenic distribution in irrigated summerrice, a location was identified from groundwater arsenic risk prone area from GIS-aided arsenic map. An in-situ low cost technology using biochars as strong adsorbent was developed from locally available bio-wastes from rice straw and toria stover. A farmers’ friendly easy to use kiln for production of biochars in field condition was fabricated and accepted overwhelmingly by the local farming community. Application of biochars at 1 to 2 percent levels applied at the conveyance channel of 45 meter long and 43 cm width, irrespective of sources, reduced the root, straw and grain arsenic content and thus the technology would be helpful in reducing arsenic entry into food chain through rice without compromising the optimum rice yield.ThesisItem Open Access CULTURABLE ENDOPHYTIC ACTINOBACTERIA: ISOLATION AND CHARACTERIZATION FROM RICE PLANTS(AAU, Jorhat, 2017-10) Devi, Yumnam Bijilaxmi; Nath, DhrubaJyotiIn the present investigation, endophytic actinobacteria were isolated from six different varieties of rice namely Aghoni Bora, Badshabhog, Basundhara, Ranjit, Joha andSolpuna. Samples were collected from 33 sites located at Golaghat and Jorhat districts of Assam. The isolates were assessed for morphological characterization, biochemical characterization and physiological features with special reference to antimicrobial activities against pathogenic fungi as well as bacteria. Finally, eleven selected isolates were subjected to 16S rDNA sequence analysis for establishment of their genotypic position. Altogether 57 isolates were obtained from six varieties of rice in Starch Casein Agar (SCA) and Casein Yeast Extract Glucose Agar (CYGA) medium. Overall, occurrence of actinobacteria colonies were more prominent in roots compared to stems and leaves. Among the six different rice varieties, the frequency of morphologically well recognized actinobacteria colonies were found to be significantly highest in Solpuna in roots (131.00 g-1), stem (117.00 g-1) and leaves (106.00 g-1). Based on distinct colony morphology and prominent growth without contamination on SCA media, 24 isolates were selected for in-vitro plant growth promoting traits. The growth of all isolates was found to be optimum at pH 7.2 and at temperature 300C ranging from 4.78 to 7.94 log cfumL-1 and 5.00 to 8.67 log cfumL-1respectively. Most of the isolates showed positive result for intracellular and extracellular enzymatic activities. 50% of the isolates showed positive result for gelatin liquefaction. All the isolates except AL2 and SL3W could hydrolyze lipid. 70.83% showed positive result for nitrate reduction. All the isolates except AL2 and SR4 showed negative reaction for catalase activity. Except AS1, SL3W and WNPR1, all the isolates illustrated positive urease activity. All the isolates displayed negative result for H2S production except AS1. 62.5% isolates could produce siderophore and all the isolates could produce hydrogen cyanide. The ability of the isolates to solubilize P was recorded after 7 and 14 days of growth. After 7 days of growth, the value ranged from 0.067 to 0.500 µg mL-1 and 0.067 to 0.633 µg mL-1 after 14 days of growth. The isolates showed similar result in IMViC (Indole, Methyl red, VogesProskaur’s and Citrate utilisation), 66.7 % isolates giving positive result for methyl red test.Rare utilization of carbon sources utilization was observed in all the isolates.Twenty two isolates showed antimicrobial activity against at least three pathogenic fungi. Isolate AS1, AL1, ABR1, BRL2, BRL3, BSS1, BSL1, SS1, SS3, SS5, SL1, SL2, SL3W, SL3Y and SL4 showed inhibition against all the four pathogenic fungi viz.Fusarium oxysporum, Rhizoctoniasolani,Curvularialunataand Sclerotiniasclerotiorum. Overall, isolates BSL1 and SL3W showed high inhibition against all the four pathogenic fungi tested.Six isolates out of twelve selectedviz. ABR1, BRL2, BSL1, SL1, SL3W and SL4 showed high inhibition against pathogenic bacteria Xanthomonasoryzae and four isolates ABR1, BRL2, BSL1 and SL1 exhibited inhibition against Erwinia sp. The inhibition zone ranged from 17 to 24 mm against Xanthomonasoryzae and 19 to 30 mm against Erwinia sp. The isolates showing high antimicrobial properties showed antibiotic resistance against few common antibiotics. Taxonomic identity of selected 11 isolates belonged to Streptomyces longispororuber, Nocardiopsissp., Streptomyces rochei, Streptomyces finlayi, Nocardiopsisalba, Streptomyces sp., Streptomyces parvulus and Streptomyces coelicolor. Most common genus was found to be Streptomyces (81.8%).In conclusion, it was established that rice plants of Assam harbors potential endophytic actinobacteria possessing multiple plant growth promoting traits with antimicrobial activities. These isolatescould be potential candidates for inclusion in integrated nutrient management and organic farming as a means of growth promoter as well as plant disease suppressor.ThesisItem Open Access SCREENING AND EVALUATION OF METHANOTROPHIC BACTERIA FROM RICE ECOSYSTEM(AAU, Jorhat, 2017-07) Phukan, Amrita; Baruah, RajenMethane (CH4) is an important greenhouse gas with 25 times more global warming potential than carbon dioxide (CO2). Rainfed/wetland rice fields are one of the major anthropogenic sources of CH4 release to the atmosphere. Therefore, there is utmost need to mitigate the methane menace. Microorganisms especially Methanotrophs play vital role for biological sink of methame through oxidation to CO2. Considering the fact, the present study was undertaken to isolate and screen novel organisms with methane oxidising properties. A total of 28 Methanotrophic bacterial cultures were isolated from 20 different rice rhizosphere samples of Jorhat district. Altogether 11 out of 28 isolates were selected as methanotrophs on the basis of their growth in Nitrate Mineral Salt (NMS) with CH4 as their sole carbon source. The 11 Methanotrophic bacterial cultures were characterized on the basis of cell morphology, carbohydrate utilization and the degree of susceptibility towards the antibiotics to assess variation within the cultures. All the isolates were screened for their methane oxidizing property and other enzyme activities viz., soluble methane monooxygenase (sMMO), particulate methane monooxygenase (pMMO) and nitrate reductase. The results showed the variation among the cultures in enzyme activities, however all the selected cultures showed methane oxidizing property to the tune of 16053.153 ± 1.333 ppm CO2 to 1787.574 ± 0.938 ppm CO2. Nitrate reductase and sMMO activity was also determined quantitatively for all the isolates to screen the efficient cultures. Specific activity of sMMO by different cultures ranged from 685.489 ± 0.494 nmol h-1 mg of protein-1 to 55.712 ± 0.659 nmol h-1 mg of protein-1. The nitrogenase enzyme activity was determined to check the biofertilizer potential of the test cultures by acetylene reduction assay. The amount of acetylene reduced to ethylene by the test isolates ranged from 8.282 ± 0.240 µmole C2H4/ml/hr to 0.015 ± 0.003 µmole C2H4/ml/hr. The bacterial strains recorded varying soil enzyme activities under soil incubation study of 30 days indicating its role in maintaining soil health. Some of the enzyme activities studied were: MBC, Dehydrogenase, Phosphomonoesterase, FDA hydrolysis, arylsulfatase and urease. The test cultures showed variation in these properties. It was observed that methane oxidation and emission highly correlated with some of the enzyme activities. For instance, Dehydrogenase was found to be the most influencing parameter for methane oxidation ( r = 0.887, P =0.001) and emission ( r = -0.611, P =0.001). Similarly, there was a significant positive correlation between sMMO activity and methane oxidation ( r = 0.536, P =0.001) but a negative correlation with methane emission ( r = -0.539, P =0.001). Based on qualitative and quantitative evaluation, the Methanotrophic bacterial cultures were selected for pot culture evaluation taking rice as test crop. The rice seedlings were inoculated with Methanotrophic bacterial cultures and grown for 35 days. The methane flux were recorded at tillering stage using closed acrylic chamber method. Methane flux recorded for different strains along with uninoculated control ranged from 3639.504 ± 2.254 µg CH4/m2/day Soil to 313.202 ± 3.314 µg CH4/m2/day Soil and also plant growth promotion was observed in all inoculated treatments over uninoculated control which was evident from increase in plant height, root length, tiller number, fresh weight and dry weight. Among the test organisms, MB 16 and MB 28 significantly reduced the methane flux over other Methanotrophs. The results further showed that other Methanotrophic cultures also performed better in reducing methane emission when compared with uninoculated control. Inoculation of MB 16 and MB 28 significantly enhanced the plant growth parameters while other Methanotrophs was either at par or higher than uninoculated control in some of the parameters. 16S rRNA gene sequences of seven methanotrophic cultures revealed that they belonged to the group ɣ-proteobacteria and α-proteobacteria representing the genera Methylomonas, Methylomicrobium, Methylosinus, Chryseobacterium and Methylocystis. The resulted sequences of the organisms were deposited in NCBI, GeneBank with accession numbers. These strains possessed the particulate (pmoA) and soluble (mmoX) methane monooxygenase gene as functional marker for detection of methanotrophs.MB 16 identified as Methylosinus sp. (Type II Methanotroph) and MB 28 identified as Methylomicrobium buryaticum (Type I methanotroph) has been considered as efficient methane oxidizing bacteria having biofertilizer and bioremediation potential which could be exploited along with other potent novel Methanotrophs as future microbial inoculants.ThesisItem Open Access SOIL FERTILITY EVALUATION IN KARIMGANJ DISTRICT OF ASSAM UNDER DIFFERENT LAND USE SYSTEMS(AAU, Jorhat, 2018-03) Choudhury, Muqsitur Rahman; Dutta, SamironThe present investigation was carried out to evaluate soil fertility status of Karimganj district of Assam under various land use systems. A total of one hundred twenty geo-referenced composite soil samples were collected from twelve different land use systems of the district. The results revealed a wide textural variation ranging from silt loam to clayey in the studied soils. The sand, silt and clay content of the soils varied from 6.3-64.5%, 7.0-59.7% and 11.2-41.3%, respectively. The clay was found significantly higher in rice based land use systems and lower in plantation based land use systems. The mean values of bulk density varied from 1.22 to 1.32 Mg m-3 in rice based LUS, 1.28 to 1.48 Mg m-3 in arable LUS and 1.20 to 1.36 Mg m-3 in plantation based LUS. Bulk density was significantly higher (1.48 Mg m-3) in uncultivated land use system and lowest (1.20 Mg m-3) recorded in forest. The mean values of particle density of the soils under all the land use systems ranged from a minimum value of 2.22 (± 0.06) Mg m-3 in forest land use to a maximum of 2.67 (± 0.07) Mg m-3 in arecanut land use system. Porosity was greater than 50% in soils under Tea and Rubber plantation and the mean value ranges from 45-50 % except in abandoned jhum land. Soil pH was found to be very strongly to moderately acidic (4.81-5.78). Barring the soils under Tea, abandoned jhum and forest, most of the soils have mean pH values more than 5.0. Organic carbon content of soils under all the land use systems was medium to high. It was highest in forest followed by abandoned jhum, tea, rubber and rice-vegetable LUS. Similar trend was also noticed in total organic carbon content of the soils. The EC of the soils was recorded as normal (< 1 dS m-1) and the variation was minimum for all the soils of twelve land use systems. The mean values of total exchangeable cations (TEC) under all the land use systems ranged from 1.22 (± 0.15) cmol(p+)kg-1 in tea land use system to 4.44 (± 0.47) cmol(p+)kg-1 in forest land use system. TEC was mostly influenced by clay content and pH of the soils. CEC of the soils ranged from 7.8 to 10.8 cmol(p+)kg-1and found to be mostly regulated by clay fraction of the soils. It was significantly highest in Forest LUS which was at par with rice-vegetable [10.6 cmol(p+)kg-1] and rice-fallow [10.3 cmol(p+)kg-1] systems. The percent base saturation of the soils in most of the LUS varied from 30 to 40%. Soils under Tea and Rubber plantation showed exceptionally lower values (< 20%). The available nitrogen content of the soils varied significantly from 183.1 to 477.7 kg ha-1. It was found medium only in four LUS (forest, abandoned jhum, arecanut and rice-vegetable) and rest were recorded for low status. The available phosphorus content was distinctly highest (23.1 kg ha-1) in forest land use system and lowest (7.9 kg ha-1) in tea LUS. Barring Tea and rubber, all the LUS exhibited medium status of available P. Available potassium content is medium in all the tree based LUS except Rubber. Soils under rice-based and arable LUS showed low status of this nutrient. Calcium and micronutrients was found sufficient but Mg and B status was low in all the LUS. Highest (23.08 mg kg-1) content of Av. S was observed on the forest land and lowest (9.65 mg kg-1) in the rubber land use system. Higher levels of carbon stock were recorded in plantation crop based land use systems particularly in forest, abandoned jhum and tea where more than 50 Mg ha-1 carbon stock was observed. Barring rice-fallow and rice-oilseed LUS, all the other LUS showed a carbon stock range of 30-40 Mg ha-1. The dominance of NH4+-N over NO3--N was observed irrespective of land use systems in the studied soils. The NH4+-N content of the soils was found greater than 50 mg kg-1 in almost all the LUS except in tea (49.05 mg kg-1) and arecanut (15.30 mg kg-1) LUS. The content of NO3--N was more than 5.0 mg kg-1 in all the LUS. It was particularly high in plantation crop based LUS (6.43 – 8.85 mg kg-1). Total N content decreased significantly from forest (0.165%) land use to rice-oilseed (0.044%) LUS. Similar to NO3--N, tree based LUS recorded higher Total N than other land use systems. Among the different P fractions, Fe-P was found to be the most dominant fraction followed by occluded P, Al- P and Ca-P. The highest amounts of Fe-P, Al-P & Occl-P were recorded in tea plantation and forest land use exhibited highest amounts of Ca-P and Total P. The different fractions of soil potassium were found high in plantation crop based LUS except the soils under rubber plantation. Mean values of water soluble, exchangeable and non exchangeable potassium of the soils were varied from 6.44 to 9.73 mg kg-1, 28.65 to 63.38 mg kg-1 and 550 to 791 mg kg-1 respectively. Abandoned jhum land recorded for the highest exchangeable and available potassium whereas forest land showed highest reserves of non-exchangeable and mineral potassium contents. Nutrient Index Values (NIV) in respect of organic carbon was high in tree based LUS like forest, abandoned jhum, rubber, tea LUS including rice-vegetable and pulse-oilseed LUS and lowest was observed in rice-fallow system whereas the NIV of organic carbon for the district was high. NIV for available N was low for the district with only three LUS (forest, abandoned jhum and arecanut) having the medium value. The NIV for available P was found medium for the district and in all the LUS except vegetable-vegetable, tea and rubber where it was low. In case of available K, only four LUS (forest, abandoned jhum, arecanut and tea) was recorded for medium NIV for potassium and others were low as similar to the low NIV value recorded for the whole district. There was a gradual decrease in SFI from forest land to other land uses. The forest maintains greater fertility, followed by uncultivated, abandoned jhum, arecanut plantation and lowest fertility was recorded in tea land use system. SEF was highest in forest, followed by abandoned jhum, arecanut plantation and least for tea. Highly significant correlations of SFI and SEF with soil physico-chemical and fertility properties indicated that these two indices can successfully be used as indicators of soil quality. Various thematic maps on different soil parameters showed that most of the soils of Karimganj district are sandy clay loam in texture (55.49%), strongly acidic in reaction (67.33%), high in organic carbon (85.07%), low in Av. N content (76.88%), medium in Av. P content (78.40%), medium in Av. K status (78.56%), high in DTPA-Zn (99.98%) and low in HWS-B (100%). A total of 250 numbers of Soil Health Cards were distributed to farmers of the district.