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20172
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Subject: Soil Sciences × End date: 2017 × Start date: 2017 ×
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    ThesisItemOpen Access
    LAND EVALUATION FOR CROP INTENSIFICATION IN BUMNOI-MORNOI WATERSHED OF KOKRAJHAR DISTRICT OF ASSAM USING REMOTE SENSING AND GIS TECHIQUES
    (AAU, Jorhat, 2017-07) Basumatary, Danswrang; Dutta, Marami
    The present study was undertaken in Bumnoi-mornoi watershed of Kokrajhar district of Assam in order to characterize and prepare soil resource maps, to study soil site suitability and to find out the related constraints for crop production. Altogether six profiles and twenty two surface samples were collected from two different physiographic units viz., alluvial plain and flood plain. The samples were analyzed for various morphological and physic-chemical properties. The dominant hue of soil colour was 10YR, except in sub surface C horizon of P1 (AP) where it was 7.5YR. Colour value ranged from 3 to 6 and chroma from 1 to 6. Yellowish red (2.5YR 4/6) to reddish yellow (7.5YR 7/6) mottles were observed in the soils. Wide variations were observed in soil textural class varying from sand to clay loam. The structure of the soil varied from medium, weak to moderate sub angular blocky at the surface to very fine to medium, week to moderate sub angular blocky, massive and single grain structure. Organic matter content in the soil varied from 0.07 to 3.13 g kg-1, the highest being observed in the surface Ap horizon of P3. Soil pH varied from 4.7 to 6.2. Sand, silt and clay contents in these soils varied from 23.3 to 89.2, 9.9 to 60, and 1.8 to 22.1 per cent, respectively. Among the exchangeable cations, Ca2+ was the dominant cation followed by Mg2+, Na+ and K+. CEC of the soils varied from 3.5 to 10.2 cmol (p+) kg-1. Available N varied from 13.44 to 448.0 kg ha-1, available P2O5 varied from 0.92 to 55.70 kg ha-1 and available K2O varied from 137.2 to 451.0 kg ha-1, respectively. The studied soils were classified as Aquic Dystrudepts (P1), Oxyaquic Dystrudepts (P2, P4), Typic Dystrudepts (P3), Aquic Udorthents (P5) and Fluvaquentic Epiaquepts (P6). The productivity of the soils for crop production varied from poor to good in alluvial plain, and poor to average in flood plain. Potential productivity varied from average to good in alluvial plain and flood plain, respectively. The co-efficient of improvement (CI) values indicated that the productivity of the alluvial plain and flood plain soils can be increased to maximum extend of 2.22 to 1.88, respectively. Soil site suitability assessment showed that the soils were moderately suitable (S2) to permanently unsuitable (N2) for Sali rice, Ahu rice, Potato and Maize. Soils were found to be very suitable (S1) to permanently not suitable (N2) for Banana. For pineapple, the soils were found to be very suitable (S1) to moderately suitable (S3). Various thematic and soil site suitability maps along with potential productivity maps of the study area were prepared using remote sensing and GIS techniques.
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    ThesisItemOpen Access
    DISSOLVED ORGANIC MATTER AND SOIL ENZYME ACTIVITY IN ORGANIC CULTIVATION OF RICE
    (AAU, Jorhat, 2017-07) Buragohain, Pubali; Nath, DhrubaJyoti
    The dissolved organic carbon (DOC), dissolved organic nitrogen (DON), reducing sugars(hexose and pentose), soluble phenols, protein, amino acids,key enzymes [arylsulfatase(ARS), phosphomonoesterase (PME), fluorescein di-acetate (FDA) β-glucosidaseand urease] contained indissolved organic matter (DOM) and biodegradability of DOM were assessed as influenced by application of organic inputs in organic rice (variety: Joha)after five years of experiment. Two extractantsviz:1.0MKCl(salt extractable organic matter, SEOM) and 5.0mM CaCl2(water extractable organic matter, WEOM) were used for extraction of DOM from the rhizosphere soils. The results indicated the significant variations of DOM under the organic inputs. Significantly highest DOC of 83.41(mg/kg) and 31.32(mg/kg) were obtained by the extractants SEOM and WEOM on application of enriched compost (EC) (@5t/ha) and compost(5t/ha) respectively. Significantly highest DON of 54.33 and 47.54(mg/kg) were obtained in the extractant SEOM and WEOM under the application of EC@5t/ha and 2.5t/ha respectively. The phenol, protein, amino acids and reducing sugars were also exhibited the significant variation under different organic inputs following the utilization of two extractants. Among the organic inputs, EC @ 5.0t/ha, @2.5t/ha and compost @5.0t/ha with biofertilizer consortium contributed significantly higher amount of enzymes in DOM. Application of EC either @ 5.0t/ha or @2.5t/ha continuously for five years could resulted significantly highest amount of PME, FDA and ARS activity while application of compost @5.0t/ha with or without biofertilizers could resulted higher content of urease and β-glucosidase activity respectively. The total organic carbon (TOC) and total nitrogen (TN) were significantly highest (12.53 g/kg and 8.60g/kg respectively) in soil under the application of EC @5.0t/ha while soil organic carbon (SOC), was significantly highest (10.60g/kg) under the application of compost@5t/ha. Likewise the fractions (F1, F2, F3 and F4) of TOC were influenced significantly by different organic inputs. The correlation matrix illustrated the significant correlation between the two extractant for ARS (0.787**),PME (0.490*) ,β-glucosidase (606**),hexose (756**), protein (0.736**) and biodegradable DOM(0.595**). DON of DOM also established significant correlations in between the two extractant but in a different way. The SOC, TOC, fraction 1 and fraction 2 of TOC illustrated significant correlation with the DOC ofSEOM while TN could show the significant correlations with DON of both the extractants. However, varied significant correlations between the SOC, TOC, fractions of TOC and TN with different components of DOM were observed under the two extractants.The biodegradability of DOM were also significantly influenced by DOC, DON,SOC, fractions of TOC, TOC and TN at varying degree under the two extractants. The favorable soil environment encouraged due to successive application of organic inputs for five years eventually reflected the improvement in rice (aromatic Joha) yield by 21.37-33.76% over unfertilized control.