Browsing by Author "Gupta, Shilpi"
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ThesisItem Open Access Dynamics of soil nitrogen and phosphorus vis-à-vis nutrient regimes in lowland rice field(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2021-02) Gupta, Shilpi; Bora, Pradip KumarAn experiment was conducted for partial fulfilment of M.Sc (SSAC) degree in the Kharif season of 2019 to study the nutrient dynamics specially the temporal fate of N and P under lowland rice cultivation at different depths. The experiment was designed in two factors randomized block design with the following objectives of determining the temporal soil solution N and P pool under different nutrient regimes and to assess the relationship of temporal soil solution N and P pools with crop uptake. Three varieties of rice viz. Ranjit (V1), CAU-R1 (V2) and Shasarang1 (V3) were considered and the nutrient regimes considered were (a) Control (T0, no fertilizers), (b) 100% RDF (T1), (c) 100% FYM (T2), and (d)50% RDF + 50% FYM (T3) .Two PVC pipes of 50 mm diameter were installed in each of the experimental plots, at 15 cm and 30 cm depths each for collecting soil solution. Plant and soil samples were collected at 60 and 120 days along with initial soil sampling to determine N and P uptake by the crops. In the experiment only two macro-nutrients, N and P were considered for the studies. N is lost in lowland ecosystem through nitrification and volatilization, denitrification and leaching processes. Losses of P was also reported through drainage water due to percolating water and leaching. The results revealed that NH4 +-N ranged in between 1.76 mglˉ¹ to 4.89 mglˉ¹ at 0-15 cm depth and in between 1.69 mglˉ¹ to 4.76 mglˉ¹ at 15-30 cm depth of soil solution. NO3 −-N ranged in between 1.51 mglˉ¹ to 4.21 mglˉ¹ at 0-15 cm depth and in between 1.41 mglˉ¹ to 4.27 mglˉ¹ at 15-30 cm depth. P ranged in between 0.55 mglˉ¹ to 1.26 mglˉ¹ at 0-15 cm depth and in between 0.47 mglˉ¹ to 1.16 mglˉ¹ at 15-30 cm depth of solution. Similar trends of nutrients were seen for SOC, Avl. N and Avl. P. Soil and Solution pH and EC was found to increase with depth of solution respectively. DOC, NH4+-N, NO3 - -N and P in soil solution was generally found to decrease with depth, however in those treatments where inorganic nutrients were applied showed a higher NO3- -N at lower depth of soil solution. In the initial stages of crop growth, solution ammonical and nitrate nitrogen is highly correlated with N uptake but in later stages, though the correlation was positive but it was not significant. However, solution P was significantly correlated with P uptake at both depths till 60 DAT, but at harvest, significance was seen only at lower depths, which might be caused due to deeper penetration of roots in soil system in search of P. From the study it can be concluded that a considerable amount of N and P were available in the solution phase making them vulnerable to move out of the crop field either through runoff or through sub-surface drainage and leaching. Crops at 60 DAT usually pass through maximum vegetative stage and has tendency for better nutrient uptake. The pattern of uptake at two critical growth stages indicate that N and P availability get reduced towards the maturity stage in solution and a better correlation was observed at 60 DAT than at 120 DAT. Thus, the null hypothesis is rejected and it can be said that there exists temporal as well as spatial trends in solution N and P pools in the soil system and has a definite positive correlation with crop uptake of nutrients.ThesisItem Open Access Evaluation of Azotobacter strains for nitrogen fixation, survival, soil fertility, plant growth and nutrient uptake by maize (Zea mays L.)(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2005-01) Gupta, Shilpi; Singh, H.P.Laboratory and greenhouse studies were undertaken to isolate, characterize and identify different strains of Azotobacter (AZO) isolated from soil. Relative performance of isolated strains and responses to inoculation with efficient Azotobacter strain and graded doses of fertilizer nitrogen with or without FYM addition were assessed in terms of plant height, fresh and dry weight of root and shoot of maize, N uptake, microbial population in soil and available N, P and K in soil at 60 and 70 days after sowing (DAS). Based on cultural, morphological and biochemical characteristics, 19 strains of Azotobacter were isolated which differed in nitrogen fixing capacity to a great extent under bacteriologically controlled condition ranging from 1.79 to 9.84 mg N fixed per 25 mL broth culture, the maximum being with AZO-NMS4 strain which was about 8 times more than the lowest nitrogen-fixing AZO-NMS7 strain. The different strains of Azotobacter significantly increased plant height, fresh and dry weight of root and shoot, uptake of N, P and K by maize shoot, available NPK in soil and population of Azotobacter, actinomycetes and fungi in soil over the uninoculated control at 60 DAS. The numbers of low, medium and high responsive strains in terms of increased shoot dry weight were 2, 11 and 6 strains, respectively. Inoculation with an efficient strain Azotobacter, FYM and graded doses of nitrogen in different combinations significantly increased plant height, fresh and dry weight of root and shoot of maize, uptake of nutrients, microbial population in soil and availability of N, P and K in soil at 70 DAS. Inoculation with Azotobacter alone, FYM alone and AZO+FYM significantly increased dry weight of maize shoot in successive significant manner which was 58.30 %, 138.47 % and 174.61 % more than the control, respectively. The maximum (328.53 % more than control) shoot dry weight was recorded with N-210 treatment which was statistically similar to AZO+FYM+N-80 treatment followed by AZO+FYM+N-60 treatment combination. Further, it has been recorded that AZO+FYM+N-60 treatment combination was statistically at par with application of N @ 120 kg ha-1 in increasing the majority of the parameters studied indicating a saving of 60 kg N ha-1 through the integrated use of biofertilizer, FYM and inorganic nitrogenous fertilizer for obtaining maximum and sustainable crop yield.