PG Thesis
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Item Synthesis and evaluation of biochar based zinc oxide(ZnO) composite as a slow release fertilizer(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2025) Malavika, J.Biochar is a carbon-rich material produced from organic residues through the pyrolysis process under limited oxygen supply. The versatile properties of biochar include high porosity, high surface area, and an abundance of surface functional groups, making it beneficial as a soil amendment, for carbon pool, for heavy metal adsorbent, as well as slow-release fertilizer. The study entitled “Synthesis and Evaluation of Biochar-Based Zinc Oxide Composite as a Slow- Release Fertilizer” was conducted in the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara during 2022-2024. This study comprised of two experiments. The first experiment, the coconut fronds (CF) were used as feedstocks for biochar production at two different temperatures, viz 450℃ and 650℃. The biochar obtained at respective temperatures was evaluated for their physicochemical properties, including pH, EC, volatile matter, ash content, and macro- and micronutrient composition, to determine variations based on temperature. The finely sieved biochar undergone surface characterisation techniques such as Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, and X-ray Diffraction (XRD) to assess surface morphology, functional groups, surface area, and crystallinity, respectively. In the experiment, from CF 450 and CF 650 biochar, corresponding biochar composites (BBZOC 450 and BBZOC 650) were prepared using a biochar-sodium hydroxide solution and a zinc nitrate-starch solution in a 1:1 ratio. The prepared BBZOC were also analysed for their physicochemical properties. The physical properties showed that CF 450 biochar had a higher recovery percentage (35.80%) than CF 650 biochar (28.30%). CF 650 biochar exhibited higher ash content (17.90%), bulk density (0.131 g/cm³), pH (10.70), EC (6.7 dS/m), and pHzpc (10.80), while CF 450 biochar had lower values for these parameters (16.66% ash content, 0.13 g/cm³ bulk density, pH 10.34, EC 4.50 dS/m, and pHzpc 9.50). The macro- and micronutrient concentrations decreased with increasing pyrolysis temperature. The mineral composition of CF 650 biochar were 55.95% carbon, 1.63% hydrogen, 0.56% nitrogen, 25.20% oxygen, 0.25% S, 0.28% P, 1.142% K, 1.54% Ca, and 2.52% Mg, along with trace amounts of Fe, Mn, Zn, Cu, and B. CF 450 biochar contained 50.86% carbon, 2.36% hydrogen, 0.4% nitrogen, 28.14% oxygen, 0.22% S, 0.22% P, 0.90% K, 1.25% Ca, and 2.26% Mg, along with trace amounts of Fe, Mn, Zn, Cu, and B. The FTIR characterisation techniques depicted the presence of more functional groups in CF 450 biochar as compared to CF 650 biochar. The XRD spectra confirmed the presence of KCl and SiO₂ in both CF 450 and CF 650, with the indication of broad wide spectra. The BET analysis exhibited a greater surface area for CF 650 biochar, with more number of pores concentrated below the 10 nm range, whereas CF 450 biochar showed more number of pores concentrated in the 10– 100 nm range. The elemental ratio analysis of biochar exhibited higher aromaticity, hydrophilicity, and polarity for CF 650 biochar than CF 450 biochar. The physico-chemical analysis of BBZOC showed a decline in the pH, with values viz. 7.36 for BBZOC 650 and 7.91 for BBZOC 450. The results also showed an increase in bulk density in the BBZOC (from 0.13 to 0.23 g/cm³ in BBZOC 650 and from 0.131 to 0.19 g/cm³ in BBZOC 450) due to the formation of zinc oxide. The surface characterisation techniques revealed an enhanced surface area with a decreased pore diameter in BBZOC 450, whereas BBZOC 650 exhibited a decreased surface area. The presence of white deposits on the BBZOC surface in SEM analysis and the appearance of 536 cm⁻¹ and 499 cm⁻¹ peaks in FTIR spectra confirmed ZnO bonding and the formation of zinc oxide on the biochar. Elemental ratio analysis indicated increased aromaticity, hydrophilicity, and polarity in BBZOC due to oxygen addition. Water absorbance, swelling ratio, equivalent water content, and water retention studies showed that BBZOC 450 exhibited slightly better water absorbance and retention compared to corresponding CF 450 biochar. In the second experiment, biochar and its corresponding BBZOC were used to study the slow-release pattern of zinc in both water and soil. In the water column study, leachates were analyzed at 1, 3, 5, 10, 15, and 30 days. Similarly, in the soil column study, leachate were analyzed at 1, 3, 5, 10, 15, 30, and 60 days using five different treatments (10 g, 20 g, 30 g, and 40 g of BBZOC). The results of soil column showed a cumulative release of zinc and zinc content were estimated as 1665.53 mg/L and 2054.09 mg/L for BBZOC 650 and BBZOC 450, respectively. In the water column study, cumulative zinc release was 273.608 mg/L and 411.480 mg/L for BBZOC 650 and BBZOC 450, respectively. The data thus obtained from both the soil and water column study picturizes that the BBZOC 450 exhibited greater zinc release compared to BBZOC 650, with the highest release at an application rate of 40 g BBZOC treatment. The results confirmed that BBZOCs can function as an efficient slow-release fertilizer, providing gradual zinc release over time.Item Standardization of spacing and fertilizer recommendation for tomato (Solanum lycopersicum L.) varieties in AEU 8(Department of Vegetable Science, College of Agriculture, Vellayani, 2024-03-02) Sreelakshmi, S; Sarada, SItem Suitability of Tunisia rock phosphate for direct application in acid rice soils of Kerala(Department of Soil Science and Agricultural Chemistry, College of Horticulture,Vellanikara, 1997) SanthoshKumar, V C; Mariam, K AA study was conducted at College of Horticulture during the period 1993-95 so as to assess the suitability of Tunisia rockphosphate for direct application in acid rice soils of Kerala as a source of P compared with single superphosphate (SSP) diammonium phosphate (DAP) and Mussoorie rockphosphate (MRP). In addition to above sources a control treatment (with no P fertilizer) and another treatment with SSP of the rate of 45 kg P2O5 ha-1) given twice (conventional practice) were also included. The P release from all the sources was monitored with an incubation experiment. In order to evaluate the residual effect of fertilizers two continuous pot culture experiments were undertaken using Triveni variety of rice. The acids soils of Kerala namely Kuttanad alluvium and laterites were used for the study. The soils showed variation in pH with submergence irrespective of the treatments. The different nutrients like N, K, Ca, Mg were higher in Kuttanad soil compared to laterite soil and was found to decrease with period of incubation. The available phosphorus content gradually increased with period of incubation and reached a peak .fit 60 to 90 days for water soluble phosphates and 90th to 120th day for rockphosphates. Comparing the two extractants, Mathew's triacid extracted more available P than that of Bray solution in both soil types. In general, Kuttanad alluvium recorded higher content of available nutrient as compared to laterite. The extent of fixation of P was higher in Kuttanad soil with Fe-P as dominant fraction while in laterite soil it was Al-P which was dominated. While evaluating pot culture experiment the different nutrients showed a decrease in soil and increase in uptake with the advancement of crop. Of the different soils Kuttanad alluvium registered a higher yield compared to laterite soil. It was found that TRP registered a comparable uptake of phosphorus and gave a comparable yield of grain and straw with other sources in laterite and Kuttanad alluvium. The residual effectiveness of rockphosphate was found to be higher than that of water soluble sources and TRP gave the highest. Of the two different type of soils Kuttanad soil showed a higher residual effectivenes and resulted in higher yield for 2nd crop while laterite soil registered a lower yield.Item Soil test crop response studies on coleus (Solenostemon rotundifolius Poir J.K Morton) in the laterite soils of Kerala(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2003) Nagarajan, M; Hassan, M AInvestigation entitled" Soil Test crop response studies on coleus in laterite soil of Kerala" consisting of two experiments namely fertility gradient experiment and STCR experiment was conducted during 2002 in the farm attached to the College of Horticulture, Vellan ikkara. Objective of the study was to develop soil test based balanced fertilizer recommendation for specific yield targets of coleus in laterite soils of kerala and provide a basis for fertilizer recommendation for maximum and economic tuber yield at varying soil test values. The fertility gradient experiment was conducted to create desired gradient in soil fertility in one and the same field by applying graded doses ofN, P, and K fertilizers and raising fodder maize var.Co.l. After development of fertility gradient, the STCR experiment was conducted in the same field with the test crop, coleus variety Nidhi.The treatment structure consisted of four levels of N (0,20,40, and 80 kg ha'), three levels of P20S (0,45 and 90 kg ha-I) and five levels of K (0, 25, 50, 100, 200 kg ha-I) along with three levels of FYM (0, 7.5 and 15 t ha-I) The nutrient requirement of coleus, variety Nidhi were estimated to be 9.15,1.38 and16.38 kg ha-I N, P20S and K20 respectively to produce one tonne of tuber. The soil efficiencies worked out as 21,46.85 and 40.85 per cent for N, . , P205 and K20 respectively for coleus in laterite soil. The contribution of nutrients from the fertilizers for coleus was calculated as 61.6,9.57 and 56.60 per cent for N, P205 and K20 respectively. From the above basic data, fertilizer prescription equation for specific yield targets of coleus variety Nidhi in the laterite soil were derived as follows, Without rVM FN =14.85T-0.34SN FP205 =14.42T-l J.21SP FK20 =28.98T-0.87SK FN, F P20S, F K20 - Fertilizer N, P20S and K20 respectively T - Target yield of tuber in t ha-I SN, SP, SK - Soil available N, P and K in' kg ha-I respectively . WithFYM FN 14.85 T - 0.34 SN - 0.34 ON 14.42 T - 11.21 SP - 3.25 OP F K20 = 28.93 T - 0.87 SK - 1.22 OK Where, ON, OP and OK are quantities ofN, P and K supplied through organic manure in kg ha" Multiple regression models calibrated with yield as dependent variable and STVs for available N, P and K and applied nutrients as independent variables had 67.4 per cent predictability. Among the three fertilizer nutrients, FN only showed the normal type (+, -, -) of response. The fertilizer adjustment equation fur v,!rying levels of soil available N for maximum tuber yield (t ha") of coleus in laterite soil was derived as FN= 168 SN, where FN is fertilizer N (kg ha"): SN is available N (kg ha-I) is soil. The behavior of applied p and K was found to produce responses other than normal and hence optimization coula not be done for fertilizer P and K at varying soil test values. Simple correlations coefficient was worked out for Nutrient uptake, soil available nutrients, applied nutrients with yield of coleus. Available nutrients -! showed higher positive correlation" than that of allied nutrients. The uptake of nutrients (N, P and K) also significantly correlated with yield of coleus. This study is useful to adjust fertilizer doses based on the specific objective and available resources of coleus farmers of the state.Item Utilization of soil test recommendations by the farmers in Trivandrum district(Department of Agricultural Extension, College of Agriculture, Vellayani, 1987) Balan, S; Muraleedhara Prasad, rItem Climate change adaptation on rice production(Academy of Climate Change Education and Research Vellanikkara, 2016) Navya, M; Sunil, K M