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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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20212
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Subject: Soil Sciences × End date: 2021 × Start date: 2021 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    ASSESSMENT OF POTASSIUM USE EFFICIENCY IN TRANSPLANTED RICE
    (2021) Seema Bhagowati; Das, Kulendra Nath
    Potassium (K) the third major essential plant nutrient with diverse roles to play in plant metabolism is required in large amount by crops and is the seventh most abundant element in the earth crust. The total K reserves are generally large in most soils but large portion of soil potassium (90 – 98%) remains chemically bound in the crystal structure of minerals and thus unavailable or slowly available for plant uptake. Based on availability to plants, potassium is categorized into four groups viz., water soluble, exchangeable, non-exchangeable/fixed and lattice K. Potassium supply to crop is a complex phenomenon involving relationships among various K fractions, potassium fixation and release patterns in soil and quantity-intensity relationships. Moreover, the net negative balance for K in current agriculture scenario is 69% which is very high as compared N (19%) and P (12%). This vast difference is partly because of crop removal where 1.5 times more K is removed than N and the application of potassium through fertilizer is considerably lower than that of N or P. Keeping these points in view, a study was carried out on “Assessment of Potassium use efficiency in transplanted rice” in Nagaon district which is famously known as the 'Rice bowl of Assam'. A series of laboratory analysis along with field experiments was carried out to assess the potassium use efficiency in transplanted rice. The soil of the experimental plot was analysed for salient characteristics such as texture including mineralogy of sand, silt and clay, pH, EC, OC, CEC, available NPK contents and various forms of K. An incubation study was conducted upon imposition of ten different treatments for a period of 150 days to know the availability of various forms of potassium in the soils at 20, 40, 60 and 90 days after incubation. After completion of incubation period, soils from various treatments were taken for study the release pattern of step K, constant rate K and cumulative K and fixation of potassium in these soils. Along with the incubation study, a field study was also conducted consecutively for two years with the same ten treatments in rice crop (var. Ranjit) with three replications in RBD design. Post harvested soils were analyzed for various physico-chemical characteristics and different K forms. Crop related data were recorded to study the effect of potassium management on growth and yield of rice. The texture of the soil of the experimental plot was clay loam with very strongly acidic pH (= 4.92). Initial status of SOC (0.91%) was high in upper surface (0-15 cm) and medium (0.65%) in lower surface (15-30cm), available N and P medium and K was low in upper surface and low available N and K and medium P was found in lower surface. X-ray diffraction study clearly indicates that clay fraction of this soil contains minerals like clay mica, mixed-layer minerals, vermiculite, smectite and kaolinite. Sand fraction is dominated by resistant minerals like quartz, zircon and weatherable minerals like mica, feldspars and chlorite and silt fraction contains same minerals as that of sand along with kaolinite. Initial water soluble K (WS-K), exchangeable K (Exch. K), non exchangeable K (Non Exch. K), lattice K and total K were 9.20, 41.00, 1020.00 8856.00 and 9480.00 mg kg-1 respectively in the upper surface (0-15 cm) of the soil. In the lower surface the values were 5.40, 28.40, 1454.00, 10222.00 and 10885.00 mg kg-1 respectively for WS-K, Exch. K, Non Exch-K, Lattice K and total K. In incubation study, where biofertilizers (T2 and T4) and organic manures (T9 and T10) were applied increase in WS-K was found with progression of the incubation period and in field study, it was highest with 21.35 mg kg-1 in the plot receiving T10 = INM Package (50% NP + Full K + 5t/ha Vermicompost) and was the lowest 8.17 mg kg-1 in the control plot. A perceptibly significant increasing trend of Exch-K was found, irrespective of the nutrient source except control treatment in incubated soil. In field condition, Exch. K corresponded to the amount of chemical K fertilizer applied and also to the INM package including microbial consortia and highest amount was observed in INM Package (50% NP + Full K + 5t/ha Vermicompost). Exchangeable K was found to be highly and significantly correlated with available K (r= 0.993**), non-exchangeable K (r=0.602*), total K (r=0.826*) and lattice K (r=0. 769**). With the increase in incubation time the non exch. K decreased in the treatments T2 = Microbial consortia (Azospirillum + PSB + KSB) @ 4 kg/ha, T4 = 100% RDF + KSB @ 4 kg/ha and T6 = Potassium nano-fertilizer @ 100 ml/1.2 L. Lower values of non-exchangeable K were recorded in all the treatments with different levels of potassium as compared to initial (1.020 mg kg-1) in the field experiment maximum being found in 100% RDF application. The increase of non exchangeable K in the control treatment with concurrent decrease in exchangeable K indicates the existence of dynamic equilibrium among different forms of potassium. Lattice K content of the treatments varied differently with different treatments but the changes were statistically insignificant in all the treatments in 40 DAI (Days after incubation) to 60 DAI and the changes was statistically at par in 60 to 90 DAI. Maximum amount of lattice was recorded in plot receiving 100% K fertilizer along with N & P fertilizers and INM components while lowest was recorded in plots which did not receive any fertilizer in field condition. The lattice K was significantly and positively correlated with available K (r= 0.791*), water soluble K (r=0.801**), exchangeable K (r=0.769*), nonexchangeable K (r=0.697*) and total K (r=0.865**). Increased levels of fertilizers brought about significant increase in total K content i.e. in the treatments where application of full dose of recommended fertilizers were done the total K tended to increase. In field condition, treatments where 100% K fertilizers were applied alone or in combination with INM components for 2 years continuously observed an increase in total K, highest being observed in T10 = 100% NP + Full K + 5 ton/ha Vermicompost) (11015.50 mg kg-1). Highly significant positive correlation values among various forms of K implied the existence of dynamic equilibrium. The amount of K released in successive extraction with boiling 1N HNO3 decreased step wisely in all treatments and reached to a constant level at 8th number of extraction. Reverse was happened in cumulative K. K release was higher in INM packages than plots received either organic or inorganic fertilizer alone. Cumulative K release was significantly correlated to lattice K (r=0.881**) suggesting that 1.0 mol L−1 HNO3 chiefly extracted K from nonexchangeable K pool in the soil. The amounts of step K of the treated soils ranged within a limit of 1837.0 to 3529.0 mg kg-1, which is high and thereby expected to be nonresponsive to K fertilization for a longer duration to the growing crops. The absolute amount of K fixed in soil progressively increased while percent K fixation decreased with increase in level of added K in all the treatments. Least percent K fixation was observed in T10 and the maximum in control. As this soil contains minerals like mica, vermiculite and smectite in clay fraction so K fixation is also high in this soil. Grain and straw yield was significantly affected by various treatments with the highest yield (= 56.22 q ha-1) in T10 which received 100% NP + Full K + 5 ton /ha vermicompost and the lowest in control. Yield was always better in INM package plots. Grain yield exhibited significant positive correlation with NPK uptake (r = 0.891**, 0.946** and 0.970**), water soluble K (r = 0.785**) exchangeable K (r = 0.897**) and available K (0.867**), suggesting their availability to rice crop. The highest potassium use efficiency (PUE) of 51.96% was found in the plot receiving 50% NP + Full K + 5 t/ha Vermicompost (T10) while the lowest of 40.49% in the plot receiving Potassium nanofertilizer @ 100 ml/1.2 L of water (T6) treatment. The information generated in the present study related to the status and distribution of different forms of potassium and its availability, releasing behavior and fixation evaluated through plant utilizable non-exchangeable K i.e. step K and constant rate K gave a general idea about the availability of K under the influences of varying doses of applied K and INM packages. Finally it can be concluded that INM Packages were found to be better for maintaining available K status, K release from none available pools and low K fixation in the soil and the resultant crop yield compared to inorganic treatments.
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    ThesisItemOpen Access
    ASSESSMENT OF SOIL ERODIBILITY AND PRODUCTIVITY POTENTIAL FOR WINTER RICE IN A TRANSECT OF JIYADHOL RIVER BASIN, ASSAM
    (2021) Saikia, Rituparna; Patgiri, D. K.
    Soil erosion is a major environmental problem in developing countries like India, where agriculture is the main economic activity of the people. The present investigation aims to assess the soil erodibility and productivity potential for winter rice in a transect of Jiyadhol river basin with respect to landform characteristics, morphometry, erosion hazard and potential for growing rice. The study area extends from 27.335 N to 27.574 N latitudes and 94.294 E to 94.540 E longitudes, covering an area of 47,389.13 ha. Based on topographical variation in satellite data, four distinct landform units were delineated which includes: piedmont plain (9,097.69 ha), upper alluvial plain (9,594.9 ha) lower alluvial plain (13,706.57 ha) and flood plain (14,977.0 ha). The drainage map identified the transect as fifth order drainage basin with higher no‘s of first order streams making it vulnerable to erosion hazard. There was significant variation of slope, physiographic structure and infiltration capacity across the basin. The mean bifurcation ratio (3.56) indicated that the basin is underlined by uniform materials and streams are branched systematically. Relatively lower value of ‗Rho‘ coefficient indicated meager capacity of hydrologic storage during the period of floods that could leads to higher runoff. The relatively higher drainage density (0.91 km km-2) could be the results of impermeable subsoil material, sparse vegetation and high relief. The drainage intensity (0.43) indicated that the basin area was highly susceptible to flooding and gully erosion. The elongation ratio, circulatory ratio, form factor ratio and shape factor indicated that the shape of the studied transect was nearly circular. Such basins are highly erosion prone as compared to elongated basins. A total of 170 no of geo-referenced surface (upto 30 cm) soil samples were collected for analyzing soil physico-chemical, hydro-physical and fertility related parameters. There was a decreasing trend in total sand and very fine sand content in soils from piedmont plain toward flood plain. Whereas, silt and clay content increases from piedmont plain towards flood plain. The textural properties of studied soils varied from loamy sand to clay loam; sandy loam was the dominant texture. The structural properties of studied soils varied from sub angular blocky to massive. Among the different landform units the highest bulk density was recorded in the piedmont plain soils (Mean 1.5 Mg m-3). The pH in the studied soils varied from very strongly acidic to slightly acidic (4.69 to 6.47). 69.4% of the total area was strongly acidic and 4.3% of the area was very strongly acidic. Cation exchange capacity, exchange capacity of clay, apparent cation exchange capacity and exchangeable cations were higher in flood plain soil which may be linked to corresponding higher clay and soil organic matter content. Likewise, the status of soil organic carbon, available nitrogen, available phosphorus and available potassium was high in soils of flood plain. Soils of flood plain exhibited higher macro-aggregation owing to higher clay and soil organic matter. However, piedmont plain soils exhibited higher microaggregate content. Soil erodibility indices viz., silt clay ratio, clay ratio, modified clay ratio, dispersion ratio, erosion ratio showed that piedmont plain soils are more susceptible to soil erosion. The geospatial assessment of their variability clearly prioritizes the areas with higher erosion susceptibility, where, suitable management practices may be undertaken to increase soil productivity. The findings from erodibility indices were further corroborated by soil loss assessment by universal soil loss equation, which revealed that 38.5 percent area was under severe soil loss. The areas in higher elevation were under higher soil loss and vice versa. The piedmont soils, affected by very severe erosion hazard (average soil loss of 34.80 t ha-1 yr-1) which might be due to dominating factors like higher relief, steep slope, lighter texture and weaker structure, hence need immediate adoption of conservation measures. The soil productivity and potentiality index was evaluated as per the procedure suggested by Riquir et al. (1970). Piedmont plain soils having productivity index values from 12.1 to 35.1 (Mean 23.0) were rated as poor to average classes. The acidic pH, low organic matter, low base saturation and coarse texture being the major limiting factors for crop production. The piedmont plain (Mean 2.01) and upper alluvial plain (Mean 1.79) soils had more coefficient of improvement as compared to lower alluvial plain (Mean 1.60) and flood plain (Mean 1.57) soils. Majority of the piedmont plain soils are found to be unsuitable for growing Sali, Ahu and Boro rice and the corresponding yield of Sali rice was also quite low. Therefore alternate crops may be grown with suitable irrigation facilities. The negative relationship of soil loss with rice yield, productivity, potentiality and suitability indicated that greater soil loss leads to decrease in productivity of soils. The potential productivity index value was higher for piedmont plain soils. Significant positive relationship was obtained between normalized difference vegetation index during peak vegetative stage with yield, soil organic matter, mean soil site suitability index for Sali rice and crop yield index in the first year of study Summarizing above results it may be concluded that the Jiyadhol river basin transect is a fifth order watershed with high vulnerability to soil erosion. Majority of the soils of the study area have high soil erodibility owing to poor soil physical properties as well as topographical position. Geospatial assessment of soil loss has clearly delineated areas with severe soil loss, hence, based on this suitable conservation measures may be effectively adopted. Moreover, while formulating site specific crop management plan GIS based thematic maps of soil properties and erodibility may be taken as ready reckoner to augment productivity, profitability and sustainability of cropping systems in the area.